diff --git a/src/ngx_pagespeed.cc b/src/ngx_pagespeed.cc
index 57e4cb975..8b9efc68b 100644
--- a/src/ngx_pagespeed.cc
+++ b/src/ngx_pagespeed.cc
@@ -484,53 +484,25 @@ enum OptionLevel {
 // we end up needing te compare.
 // TODO(oschaaf): this duplication is a short term solution.
 const char* const global_only_options[] = {
-  "BlockingRewriteKey",
-  "CacheFlushFilename",
-  "CacheFlushPollIntervalSec",
-  "DangerPermitFetchFromUnknownHosts",
-  "CriticalImagesBeaconEnabled",
-  "ExperimentalFetchFromModSpdy",
   "FetcherTimeoutMs",
-  "FetchHttps",
-  "FetchWithGzip",
-  "FileCacheCleanIntervalMs",
-  "FileCacheInodeLimit",
-  "FileCachePath",
-  "FileCacheSizeKb",
+  "FetchProxy",
   "ForceCaching",
-  "ImageMaxRewritesAtOnce",
+  "GeneratedFilePrefix",
   "ImgMaxRewritesAtOnce",
   "InheritVHostConfig",
   "InstallCrashHandler",
-  "LRUCacheByteLimit",
-  "LRUCacheKbPerProcess",
-  "MaxCacheableContentLength",
-  "MemcachedServers",
-  "MemcachedThreads",
-  "MemcachedTimeoutUs",
   "MessageBufferSize",
   "NumRewriteThreads",
   "NumExpensiveRewriteThreads",
-  "RateLimitBackgroundFetches",
-  "ReportUnloadTime",
-  "RespectXForwardedProto",
-  "SharedMemoryLocks",
-  "SlurpDirectory",
-  "SlurpFlushLimit",
-  "SlurpReadOnly",
-  "SupportNoScriptEnabled",
-  "StatisticsLoggingChartsCSS",
-  "StatisticsLoggingChartsJS",
-  "TestProxy",
-  "TestProxySlurp",
   "TrackOriginalContentLength",
-  "UsePerVHostStatistics",
-  "XHeaderValue",
+  "UsePerVHostStatistics",  // TODO(anupama): What to do about "No longer used"
+  "BlockingRewriteRefererUrls",
+  "CreateSharedMemoryMetadataCache",
   "LoadFromFile",
   "LoadFromFileMatch",
   "LoadFromFileRule",
   "LoadFromFileRuleMatch",
-  "UseNativeFetcher"
+  "UseNativeFetcher"  // TODO(anupama): Ask Jeff about this one.
 };
 
 bool ps_is_global_only_option(const StringPiece& option_name) {
diff --git a/test/nginx_system_test.sh b/test/nginx_system_test.sh
index 1c258e0ce..a85db890c 100755
--- a/test/nginx_system_test.sh
+++ b/test/nginx_system_test.sh
@@ -200,6 +200,37 @@ else
   fi
 fi
 
+# Helper methods used by downstream caching tests.
+
+# Helper method that does a wget and verifies that the rewriting status matches
+# the $1 argument that is passed to this method.
+check_rewriting_status() {
+  $WGET $WGET_ARGS $CACHABLE_HTML_LOC > $OUT_CONTENTS_FILE
+  if $1; then
+    check zgrep -q "pagespeed.ic" $OUT_CONTENTS_FILE
+  else
+    check_not zgrep -q "pagespeed.ic" $OUT_CONTENTS_FILE
+  fi
+  # Reset WGET_ARGS.
+  WGET_ARGS=""
+}
+
+# Helper method that obtains a gzipped response and verifies that rewriting
+# has happened. Also takes an extra parameter that identifies extra headers
+# to be added during wget.
+check_for_rewriting() {
+  WGET_ARGS="$GZIP_WGET_ARGS $1"
+  check_rewriting_status true
+}
+
+# Helper method that obtains a gzipped response and verifies that no rewriting
+# has happened. Also takes an extra parameter that identifies extra headers
+# to be added during wget.
+check_for_no_rewriting() {
+  WGET_ARGS="$GZIP_WGET_ARGS $1"
+  check_rewriting_status false
+}
+
 if $RUN_TESTS; then
   echo "Starting tests"
 else
@@ -236,6 +267,7 @@ if $USE_VALGRIND; then
 ~prioritize_critical_css~
 ~IPRO flow uses cache as expected.~
 ~IPRO flow doesn't copy uncacheable resources multiple times.~
+~inline_unauthorized_resources allows unauthorized css selectors~
 "
 fi
 
@@ -277,10 +309,15 @@ if [ "$NATIVE_FETCHER" = "on" ]; then
   echo "Native fetcher doesn't support PURGE requests and so we can't use or"
   echo "test downstream caching."
 else
-  CACHABLE_HTML_LOC="${SECONDARY_HOSTNAME}/mod_pagespeed_test/cachable_rewritten_html"
+  CACHABLE_HTML_LOC="http://${SECONDARY_HOSTNAME}/mod_pagespeed_test/cachable_rewritten_html"
+  CACHABLE_HTML_LOC+="/downstream_caching.html"
   TMP_LOG_LINE="proxy_cache.example.com GET /purge/mod_pagespeed_test/cachable_rewritten_"
   PURGE_REQUEST_IN_ACCESS_LOG=$TMP_LOG_LINE"html/downstream_caching.html.*(200)"
 
+  OUT_CONTENTS_FILE="$OUTDIR/gzipped.html"
+  OUT_HEADERS_FILE="$OUTDIR/headers.html"
+  GZIP_WGET_ARGS="-q -S --header=Accept-Encoding:gzip -o $OUT_HEADERS_FILE -O - "
+
   # Number of downstream cache purges should be 0 here.
   CURRENT_STATS=$($WGET_DUMP $STATISTICS_URL)
   check_from "$CURRENT_STATS" egrep -q \
@@ -288,11 +325,11 @@ else
 
   # The 1st request results in a cache miss, non-rewritten response
   # produced by pagespeed code and a subsequent purge request.
+  # Because of the random bypassing of the cache (required for beaconing
+  # integration), this request could result in a BYPASS as well.
   start_test Check for case where rewritten cache should get purged.
-  WGET_ARGS="--header=Host:proxy_cache.example.com"
-  OUT=$($WGET_DUMP $WGET_ARGS $CACHABLE_HTML_LOC/downstream_caching.html)
-  check_not_from "$OUT" egrep -q "pagespeed.ic"
-  check_from "$OUT" egrep -q "X-Cache: MISS"
+  check_for_no_rewriting "--header=Host:proxy_cache.example.com"
+  check egrep -q "X-Cache: MISS|BYPASS" $OUT_HEADERS_FILE
   fetch_until $STATISTICS_URL \
     'grep -c downstream_cache_purge_attempts:[[:space:]]*1' 1
 
@@ -305,12 +342,12 @@ else
 
   # The 2nd request results in a cache miss (because of the previous purge),
   # rewritten response produced by pagespeed code and no new purge requests.
+  # Because of the random bypassing of the cache (required for beaconing
+  # integration), this request could result in a BYPASS as well.
   start_test Check for case where rewritten cache should not get purged.
-  BLOCKING_WGET_ARGS=$WGET_ARGS" --header=X-PSA-Blocking-Rewrite:psatest"
-  OUT=$($WGET_DUMP $BLOCKING_WGET_ARGS \
-        $CACHABLE_HTML_LOC/downstream_caching.html)
-  check_from "$OUT" egrep -q "pagespeed.ic"
-  check_from "$OUT" egrep -q "X-Cache: MISS"
+  check_for_rewriting "--header=Host:proxy_cache.example.com \
+                      --header=X-PSA-Blocking-Rewrite:psatest"
+  check egrep -q "X-Cache: MISS|BYPASS" $OUT_HEADERS_FILE
   CURRENT_STATS=$($WGET_DUMP $STATISTICS_URL)
   check_from "$CURRENT_STATS" egrep -q \
     "downstream_cache_purge_attempts:[[:space:]]*1"
@@ -320,12 +357,25 @@ else
   # now present in cache), rewritten response served out from cache and not
   # by pagespeed code and no new purge requests.
   start_test Check for case where there is a rewritten cache hit.
-  OUT=$($WGET_DUMP $WGET_ARGS $CACHABLE_HTML_LOC/downstream_caching.html)
-  check_from "$OUT" egrep -q "pagespeed.ic"
-  check_from "$OUT" egrep -q "X-Cache: HIT"
+  check_for_rewriting "--header=Host:proxy_cache.example.com"
+  check egrep -q "X-Cache: HIT" $OUT_HEADERS_FILE
   fetch_until $STATISTICS_URL \
     'grep -c downstream_cache_purge_attempts:[[:space:]]*1' 1
   check [ $(grep -ce "$PURGE_REQUEST_IN_ACCESS_LOG" $ACCESS_LOG) = 1 ];
+
+  # Enable one of the beaconing dependent filters and verify interaction
+  # between beaconing and downstream caching logic, by verifying that
+  # whenever beaconing code is present in the rewritten page, the
+  # output is also marked as a cache-miss, indicating that the instrumentation
+  # was done by the backend.
+  start_test Check whether beaconing is accompanied by a BYPASS always.
+  WGET_ARGS="-S --header=Host:proxy_cache.example.com"
+  CACHABLE_HTML_LOC+="?PageSpeedFilters=lazyload_images"
+  fetch_until -gzip $CACHABLE_HTML_LOC \
+      "zgrep -c \"pagespeed\.CriticalImages\.Run\"" 1
+  check egrep -q 'X-Cache: BYPASS' $WGET_OUTPUT
+  check fgrep -q 'Cache-Control: no-cache, max-age=0' $WGET_OUTPUT
+
 fi
 
 start_test Check for correct default X-Page-Speed header format.
@@ -531,6 +581,18 @@ sleep .1
 OUT=$($FETCH_CMD)
 check_not_from "$OUT" fgrep "<style>"
 
+# Tests that we get instant ipro rewrites with LoadFromFile and
+# InPlaceWaitForOptimized get us first-pass rewrites.
+start_test instant ipro with InPlaceWaitForOptimized and LoadFromFile
+echo $WGET_DUMP $TEST_ROOT/ipro/instant/wait/purple.css
+OUT=$($WGET_DUMP $TEST_ROOT/ipro/instant/wait/purple.css)
+check_from "$OUT" fgrep -q 'body{background:#9370db}'
+
+start_test instant ipro with ModPagespeedInPlaceRewriteDeadline and LoadFromFile
+echo $WGET_DUMP $TEST_ROOT/ipro/instant/deadline/purple.css
+OUT=$($WGET_DUMP $TEST_ROOT/ipro/instant/deadline/purple.css)
+check_from "$OUT" fgrep -q 'body{background:#9370db}'
+
 # If DisableRewriteOnNoTransform is turned off, verify that the rewriting
 # applies even if Cache-control: no-transform is set.
 start_test rewrite on Cache-control: no-transform
@@ -1773,8 +1835,8 @@ check_from "$RESOURCE_HEADERS"  egrep -q 'Cache-Control: max-age=31536000'
 
 # Test critical CSS beacon injection, beacon return, and computation.  This
 # requires UseBeaconResultsInFilters() to be true in rewrite_driver_factory.
-# NOTE: must occur after cache flush on a repeat run.  All repeat runs now
-# run the cache flush test.
+# NOTE: must occur after cache flush, which is why it's in this embedded
+# block.  The flush removes pre-existing beacon results from the pcache.
 test_filter prioritize_critical_css
 fetch_until -save $URL 'fgrep -c pagespeed.criticalCssBeaconInit' 1
 check [ $(fgrep -o ".very_large_class_name_" $FETCH_FILE | wc -l) -eq 36 ]
@@ -1782,7 +1844,8 @@ CALL_PAT=".*criticalCssBeaconInit("
 SKIP_ARG="[^,]*,"
 CAPTURE_ARG="'\([^']*\)'.*"
 BEACON_PATH=$(sed -n "s/${CALL_PAT}${CAPTURE_ARG}/\1/p" $FETCH_FILE)
-ESCAPED_URL=$(sed -n "s/${CALL_PAT}${SKIP_ARG}${CAPTURE_ARG}/\1/p" $FETCH_FILE)
+ESCAPED_URL=$( \
+  sed -n "s/${CALL_PAT}${SKIP_ARG}${CAPTURE_ARG}/\1/p" $FETCH_FILE)
 OPTIONS_HASH=$( \
   sed -n "s/${CALL_PAT}${SKIP_ARG}${SKIP_ARG}${CAPTURE_ARG}/\1/p" $FETCH_FILE)
 NONCE=$( \
@@ -1805,7 +1868,6 @@ fetch_until $URL \
   'grep -c <style>[.]blue{[^}]*}[.]bold{[^}]*}</style>' 1
 fetch_until -save $URL \
   'grep -c <style>[.]foo{[^}]*}</style>' 1
-
 # The last one should also have the other 3, too.
 check [ `grep -c '<style>[.]blue{[^}]*}</style>' $FETCH_UNTIL_OUTFILE` = 1 ]
 check [ `grep -c '<style>[.]big{[^}]*}</style>' $FETCH_UNTIL_OUTFILE` = 1 ]
@@ -1860,14 +1922,16 @@ OUT1=$(http_proxy=$SECONDARY_HOSTNAME \
 check_not_from "$OUT1" egrep -q 'pagespeed\.CriticalImages\.Run'
 check_from "$OUT1" grep -q "Cache-Control: private, max-age=3000"
 # 2. We get an instrumented page if the correct key is present.
-OUT2=$(http_proxy=$SECONDARY_HOSTNAME\
-          $WGET_DUMP $WGET_ARGS\
+OUT2=$(http_proxy=$SECONDARY_HOSTNAME \
+          $WGET_DUMP $WGET_ARGS \
+          --header="X-PSA-Blocking-Rewrite: psatest" \
           --header="PS-ShouldBeacon: random_rebeaconing_key" $URL)
 check_from "$OUT2" egrep -q "pagespeed\.CriticalImages\.Run"
 check_from "$OUT2" grep -q "Cache-Control: max-age=0, no-cache"
 # 3. We do not get an instrumented page if the wrong key is present.
-OUT3=$(http_proxy=$SECONDARY_HOSTNAME\
-          $WGET_DUMP $WGET_ARGS\
+OUT3=$(http_proxy=$SECONDARY_HOSTNAME \
+          $WGET_DUMP $WGET_ARGS \
+          --header="X-PSA-Blocking-Rewrite: psatest" \
           --header="PS-ShouldBeacon: wrong_rebeaconing_key" $URL)
 check_not_from "$OUT3" egrep -q "pagespeed\.CriticalImages\.Run"
 check_from "$OUT3" grep -q "Cache-Control: private, max-age=3000"
@@ -1884,15 +1948,15 @@ OUT1=$(http_proxy=$SECONDARY_HOSTNAME \
 check_not_from "$OUT1" egrep -q 'pagespeed\.criticalCssBeaconInit'
 check_from "$OUT1" grep -q "Cache-Control: private, max-age=3000"
 # 2. We get an instrumented page if the correct key is present.
-OUT2=$(http_proxy=$SECONDARY_HOSTNAME\
-          $WGET_DUMP $WGET_ARGS\
+OUT2=$(http_proxy=$SECONDARY_HOSTNAME \
+          $WGET_DUMP $WGET_ARGS \
           --header 'X-PSA-Blocking-Rewrite: psatest'\
           --header="PS-ShouldBeacon: random_rebeaconing_key" $URL)
 check_from "$OUT2" grep -q "Cache-Control: max-age=0, no-cache"
 check_from "$OUT2" egrep -q "pagespeed\.criticalCssBeaconInit"
 # 3. We do not get an instrumented page if the wrong key is present.
 WGET_ARGS="--header=\"PS-ShouldBeacon: wrong_rebeaconing_key\""
-OUT3=$(http_proxy=$SECONDARY_HOSTNAME\
+OUT3=$(http_proxy=$SECONDARY_HOSTNAME \
           $WGET_DUMP $WGET_ARGS $URL)
 check_not_from "$OUT3" egrep -q "pagespeed\.criticalCssBeaconInit"
 check_from "$OUT3" grep -q "Cache-Control: private, max-age=3000"
@@ -1961,7 +2025,7 @@ check_from "$OUT" egrep -q "HTTP/1[.]. 204"
 http_proxy=$SECONDARY_HOSTNAME \
   fetch_until -save -recursive $URL 'fgrep -c pagespeed_lazy_src=' 1
 
-test_filter prioritize_critical_css
+test_filter prioritize_critical_css with unauthorized resources
 
 start_test no critical selectors chosen from unauthorized resources
 URL="$TEST_ROOT/unauthorized/prioritize_critical_css.html"
@@ -1974,7 +2038,7 @@ check [ $(fgrep -c "gsc-completion-selected" $FETCH_FILE) -eq 1 ]
 # a) no selectors from the unauthorized @ import (e.g .maia-display) should
 #    appear in the selector list.
 check_not fgrep -q "maia-display" $FETCH_FILE
-# b) no selectors from the authorized @ import (e.g .red) should
+# b) no selectors from the authorized @ import (e.g .interesting_color) should
 #    appear in the selector list because it won't be flattened.
 check_not fgrep -q "interesting_color" $FETCH_FILE
 # c) selectors that don't depend on flattening should appear in the selector
@@ -1994,11 +2058,12 @@ start_test inline_unauthorized_resources allows unauthorized css selectors
 HOST_NAME="http://unauthorizedresources.example.com"
 URL="$HOST_NAME/mod_pagespeed_test/unauthorized/prioritize_critical_css.html"
 URL+="?PageSpeedFilters=prioritize_critical_css,debug"
-http_proxy=$SECONDARY_HOSTNAME \
-   fetch_until -save $URL 'fgrep -c pagespeed.criticalCssBeaconInit' 3
-# gsc-completion-selected strng should occur once in the html and once in the
+# gsc-completion-selected string should occur once in the html and once in the
 # selector list.
-check [ $(fgrep -c "gsc-completion-selected" $FETCH_FILE) -eq 2 ]
+http_proxy=$SECONDARY_HOSTNAME \
+   fetch_until -save $URL 'fgrep -c gsc-completion-selected' 2
+# Verify that this page had beaconing javascript on it.
+check [ $(fgrep -c "pagespeed.criticalCssBeaconInit" $FETCH_FILE) -eq 3 ]
 # From the css file containing an unauthorized @import line,
 # a) no selectors from the unauthorized @ import (e.g .maia-display) should
 #    appear in the selector list.
@@ -2011,42 +2076,6 @@ check_not fgrep -q "interesting_color" $FETCH_FILE
 check [ $(fgrep -c "non_flattened_selector" $FETCH_FILE) -eq 1 ]
 check grep -q "$EXPECTED_IMPORT_FAILURE_LINE" $FETCH_FILE
 
-# Test critical CSS beacon injection, beacon return, and computation.  This
-# requires UseBeaconResultsInFilters() to be true in rewrite_driver_factory.
-# NOTE: must occur after cache flush, which is why it's in this embedded
-# block.  The flush removes pre-existing beacon results from the pcache.
-test_filter prioritize_critical_css
-fetch_until -save $URL 'fgrep -c pagespeed.criticalCssBeaconInit' 1
-check [ $(fgrep -o ".very_large_class_name_" $FETCH_FILE | wc -l) -eq 36 ]
-CALL_PAT=".*criticalCssBeaconInit("
-SKIP_ARG="[^,]*,"
-CAPTURE_ARG="'\([^']*\)'.*"
-BEACON_PATH=$(sed -n "s/${CALL_PAT}${CAPTURE_ARG}/\1/p" $FETCH_FILE)
-ESCAPED_URL=$( \
-  sed -n "s/${CALL_PAT}${SKIP_ARG}${CAPTURE_ARG}/\1/p" $FETCH_FILE)
-OPTIONS_HASH=$( \
-  sed -n "s/${CALL_PAT}${SKIP_ARG}${SKIP_ARG}${CAPTURE_ARG}/\1/p" $FETCH_FILE)
-NONCE=$( \
-  sed -n "s/${CALL_PAT}${SKIP_ARG}${SKIP_ARG}${SKIP_ARG}${CAPTURE_ARG}/\1/p" \
-  $FETCH_FILE)
-BEACON_URL="http://${HOSTNAME}${BEACON_PATH}?url=${ESCAPED_URL}"
-BEACON_DATA="oh=${OPTIONS_HASH}&n=${NONCE}&cs=.big,.blue,.bold,.foo"
-run_wget_with_args --no-http-keep-alive --post-data "$BEACON_DATA" "$BEACON_URL"
-# Now make sure we see the correct critical css rules.
-fetch_until $URL \
-  'grep -c <style>[.]blue{[^}]*}</style>' 1
-fetch_until $URL \
-  'grep -c <style>[.]big{[^}]*}</style>' 1
-fetch_until $URL \
-  'grep -c <style>[.]blue{[^}]*}[.]bold{[^}]*}</style>' 1
-fetch_until -save $URL \
-  'grep -c <style>[.]foo{[^}]*}</style>' 1
-# The last one should also have the other 3, too.
-check [ `grep -c '<style>[.]blue{[^}]*}</style>' $FETCH_UNTIL_OUTFILE` = 1 ]
-check [ `grep -c '<style>[.]big{[^}]*}</style>' $FETCH_UNTIL_OUTFILE` = 1 ]
-check [ `grep -c '<style>[.]blue{[^}]*}[.]bold{[^}]*}</style>' \
-  $FETCH_UNTIL_OUTFILE` = 1 ]
-
 
 start_test keepalive with html rewriting
 keepalive_test "keepalive-html.example.com"\
@@ -2084,7 +2113,7 @@ keepalive_test "keepalive-static.example.com"\
 # are combined.
 test_filter combine_css Maximum size of combined CSS.
 QUERY_PARAM="PageSpeedMaxCombinedCssBytes=57"
-URL="$URL?$QUERY_PARAM"
+URL="$URL&$QUERY_PARAM"
 # We should get the first two files to be combined...
 fetch_until -save $URL 'grep -c styles/yellow.css+blue.css.pagespeed.' 1
 # ... but 3rd and 4th should be standalone
@@ -2314,7 +2343,7 @@ if $USE_VALGRIND; then
     # It is possible that there are still ProxyFetches outstanding
     # at this point in time. Give them a few extra seconds to allow
     # them to finish, so they will not generate valgrind complaints
-    sleep 3
+    sleep 30
     kill -s quit $VALGRIND_PID
     wait
     # Clear the previously set trap, we don't need it anymore.
diff --git a/test/pagespeed_test.conf.template b/test/pagespeed_test.conf.template
index 6c2c6a1e7..83ac19a68 100644
--- a/test/pagespeed_test.conf.template
+++ b/test/pagespeed_test.conf.template
@@ -28,6 +28,17 @@ http {
   proxy_temp_path "@@TMP_PROXY_CACHE@@";
 
   root "@@SERVER_ROOT@@";
+
+  # Block 5a: Decide on Cache-Control header value to use for outgoing
+  # response.
+  # Map new_cache_control_header_val to "no-cache, max-age=0" if the
+  # content is html and use the original Cache-Control header value
+  # in all other cases.
+  map $upstream_http_content_type $new_cache_control_header_val {
+    default $upstream_http_cache_control;
+    "~*text/html" "no-cache, max-age=0";
+  }
+
   pagespeed UsePerVHostStatistics on;
   pagespeed InPlaceResourceOptimization on;
   pagespeed CreateSharedMemoryMetadataCache "@@SHM_CACHE@@" 8192;
@@ -64,6 +75,7 @@ http {
   @@RESOLVER@@
 
   server {
+    # Block 1:  Basic port, server_name definitions.
     # This server represents the external caching layer server which
     # receives user requests and proxies them to the upstream server
     # running on the PRIMARY_PORT when the response is not available in
@@ -72,58 +84,110 @@ http {
     server_name proxy_cache.example.com;
     pagespeed FileCachePath "@@FILE_CACHE@@";
 
+    # Disable PageSpeed on this server.
     pagespeed off;
 
-    set $ua_dependent_ps_capability_list "";
-    set $bypass_cache 1;
+    # Block 2: Define prefix for proxy_cache_key based on the UserAgent.
+
+    # Define placeholder PS-CapabilityList header values for large and small
+    # screens with no UA dependent optimizations. Note that these placeholder
+    # values should not contain any of ll, ii, dj, jw or ws, since these
+    # codes will end up representing optimizations to be supported for the
+    # request.
+    set $default_ps_capability_list_for_large_screens "LargeScreen.SkipUADependentOptimizations";
+    set $default_ps_capability_list_for_small_screens "TinyScreen.SkipUADependentOptimizations";
+
+    # As a fallback, the PS-CapabilityList header that is sent to the upstream
+    # PageSpeed server should be for a large screen device with no browser
+    # specific optimizations.
+    set $ps_capability_list $default_ps_capability_list_for_large_screens;
+
+    # Cache-fragment 1: Desktop User-Agents that support lazyload_images (ll),
+    # inline_images (ii) and defer_javascript (dj).
+    # Note: Wget is added for testing purposes only.
     if ($http_user_agent ~* "Chrome/|Firefox/|MSIE |Safari|Wget") {
-      # User Agents that support lazyload-images (ll), inline-images (ii) and
-      # defer-javascript (dj).
-      set $ua_dependent_ps_capability_list "ll,ii,dj:";
-      set $bypass_cache 0;
+      set $ps_capability_list "ll,ii,dj:";
     }
+    # Cache-fragment 2: Desktop User-Agents that support lazyload_images (ll),
+    # inline_images (ii), defer_javascript (dj), webp (jw) and lossless_webp
+    # (ws).
     if ($http_user_agent ~*
         "Chrome/[2][3-9]+\.|Chrome/[[3-9][0-9]+\.|Chrome/[0-9]{3,}\.") {
-      # User Agents that support lazyload-images (ll), inline-images (ii),
-      # defer-javascript (dj), webp (jw) and webp-lossless (ws).
-      set $ua_dependent_ps_capability_list "ll,ii,dj,jw,ws:";
-      set $bypass_cache 0;
+      set $ps_capability_list "ll,ii,dj,jw,ws:";
+    }
+    # Cache-fragment 3: This fragment contains (a) Desktop User-Agents that
+    # match fragments 1 or 2 but should not because they represent older
+    # versions of certain browsers or bots and (b) Tablet User-Agents that
+    # correspond to large screens. These will only get optimizations that work
+    # on all browsers and use image compression qualities applicable to large
+    # screens. Note that even Tablets that are capable of supporting inline or
+    # webp images, e.g. Android 4.1.2, will not get these advanced
+    # optimizations.
+    if ($http_user_agent ~* "Firefox/[1-2]\.|MSIE [5-8]\.|bot|Yahoo!|Ruby|RPT-HTTPClient|(Google \(\+https\:\/\/developers\.google\.com\/\+\/web\/snippet\/\))|Android|iPad|TouchPad|Silk-Accelerated|Kindle Fire") {
+      set $ps_capability_list $default_ps_capability_list_for_large_screens;
+    }
+    # Cache-fragment 4: Mobiles and small screen Tablets will use image compression
+    # qualities applicable to small screens, but all other optimizations will be
+    # those that work on all browsers.
+    if ($http_user_agent ~* "Mozilla.*Android.*Mobile*|iPhone|BlackBerry|Opera Mobi|Opera Mini|SymbianOS|UP.Browser|J-PHONE|Profile/MIDP|portalmmm|DoCoMo|Obigo|Galaxy Nexus|GT-I9300|GT-N7100|HTC One|Nexus [4|7|S]|Xoom|XT907") {
+      set $ps_capability_list $default_ps_capability_list_for_small_screens;
     }
 
-    # All User Agents that represent
-    # 1) mobiles
-    # 2) tablets
-    # 3) desktop browsers that do not have defer-javascript capability at a minimum
-    # are made to go to the pagespeed server directly bypassing the proxy_cache.
-    if ($http_user_agent ~* "Firefox/[1-2]\.|MSIE [5-8]\.") {
-      set $ua_dependent_ps_capability_list "";
-      set $bypass_cache 1;
+    # Block 3a: Bypass the cache for .pagespeed. resource. PageSpeed has its own
+    # cache for these, and these could bloat up the caching layer.
+    if ($uri ~ "\.pagespeed\.([a-z]\.)?[a-z]{2}\.[^.]{10}\.[^.]+") {
+      set $bypass_cache "1";
     }
-    if ($http_user_agent ~* "Mozilla.*Android.*Mobile*|iPhone|BlackBerry|Opera Mobi|Opera Mini|SymbianOS|UP.Browser|J-PHONE|Profile/MIDP|portalmmm|DoCoMo|Obigo") {
-      # These are Mobile User Agents. We don't cache responses for these.
-      set $ua_dependent_ps_capability_list "";
-      set $bypass_cache 1;
-    }
-    if ($http_user_agent ~* "Android|iPad|TouchPad|Silk-Accelerated|Kindle Fire") {
-      # These are Tablet User Agents. We don't cache responses for these.
-      set $ua_dependent_ps_capability_list "";
+
+    set_random $rand 0 100;
+    set $should_beacon_header_val "";
+    if ($rand ~* "^[0-4]$") {
+      set $should_beacon_header_val "random_rebeaconing_key";
       set $bypass_cache 1;
     }
 
+    # Block 3b: Only cache responses to clients that support gzip.  Most clients
+    # do, and the cache holds much more if it stores gzipped responses.
+    if ($http_accept_encoding !~* gzip) {
+      set $bypass_cache "1";
+    }
+
+    # Block 4: Location block for purge requests.
     location ~ /purge(/.*) {
-      allow all;
-      proxy_cache_purge htmlcache $ua_dependent_ps_capability_list$1$is_args$args;
+      allow 127.0.0.1;
+      deny all;
+      proxy_cache_purge htmlcache $ps_capability_list$1$is_args$args;
     }
 
+    # Block 6: Location block with proxy_cache directives.
     location /mod_pagespeed_test/cachable_rewritten_html/ {
+      # 1: Upstream PageSpeed server is running at localhost:8050.
       proxy_pass http://localhost:@@PRIMARY_PORT@@;
-      proxy_set_header Host $host;
-      proxy_cache_valid 200 30s;
+      # 2: Use htmlcache as the zone for caching.
       proxy_cache htmlcache;
-      proxy_ignore_headers Cache-Control;
-      add_header X-Cache $upstream_cache_status;
-      proxy_cache_key $ua_dependent_ps_capability_list$uri$is_args$args;
+      # 3: Bypass requests that correspond to .pagespeed. resources
+      # or clients that do not support gzip etc.
       proxy_cache_bypass $bypass_cache;
+      # 4: Use the redefined proxy_cache_key and make sure the /purge/
+      # block uses the same key.
+      proxy_cache_key $ps_capability_list$uri$is_args$args;
+      # 5: Forward Host header to upstream server.
+      proxy_set_header Host $host;
+      # 6: Set the PS-CapabilityList header for PageSpeed server to respect.
+      proxy_set_header PS-CapabilityList $ps_capability_list;
+      add_header PS-CapabilityList $ps_capability_list;
+      # 7: Add a header for identifying cache hits/misses/expires. This is
+      # for debugging purposes only and can be commented out in production.
+      add_header X-Cache $upstream_cache_status;
+
+      # Block 5b: Override Cache-Control headers as needed.
+      # Hide the upstream cache control header.
+      proxy_hide_header Cache-Control;
+      # Add the inferred Cache-Control header.
+      add_header Cache-Control $new_cache_control_header_val;
+
+      proxy_set_header PS-ShouldBeacon $should_beacon_header_val;
+      proxy_hide_header PS-ShouldBeacon;
     }
   }
 
@@ -716,11 +780,14 @@ http {
       # in the proxy_cache layer.
       pagespeed DownstreamCachePurgeMethod "GET";
       pagespeed DownstreamCachePurgeLocationPrefix "http://localhost:@@SECONDARY_PORT@@/purge";
+      pagespeed DownstreamCacheRebeaconingKey "random_rebeaconing_key";
       # We use a very small deadline here to force the rewriting to not complete
       # in the very first attempt.
       pagespeed RewriteDeadlinePerFlushMs 1;
       pagespeed RewriteLevel PassThrough;
-      pagespeed EnableFilters collapse_whitespace,extend_cache,recompress_images,convert_jpeg_to_webp,defer_javascript;
+      pagespeed EnableFilters collapse_whitespace,extend_cache,recompress_images;
+      pagespeed CriticalImagesBeaconEnabled true;
+      add_header Cache-Control "public, max-age=100";
     }
 
     location /mod_pagespeed_test/disable_no_transform/index.html {
@@ -865,6 +932,20 @@ http {
       expires 5m;
     }
 
+    location /mod_pagespeed_test/ipro/instant/wait/ {
+      pagespeed InPlaceWaitForOptimized on;
+      # TODO: Valgrind runs pass only if the below line is uncommented.
+      #pagespeed InPlaceRewriteDeadlineMs 1000;
+    }
+
+    location /mod_pagespeed_test/ipro/instant/deadline/ {
+      pagespeed InPlaceRewriteDeadlineMs -1;
+    }
+
+    pagespeed LoadFromFile
+        "http://localhost:@@PRIMARY_PORT@@/mod_pagespeed_test/ipro/instant/"
+        "@@SERVER_ROOT@@/mod_pagespeed_test/ipro/instant/";
+
     pagespeed EnableFilters remove_comments;
 
     # Test LoadFromFile mapping by mapping one dir to another.