Be more defensive about examining protobuf fields that might not be initialized.

net/instaweb/rewriter/beacon_critical_images_finder.cc

@@ -19,6 +19,7 @@
 
 #include "base/logging.h"
 #include "net/instaweb/rewriter/critical_images.pb.h"
+#include "net/instaweb/rewriter/critical_keys.pb.h"
 #include "net/instaweb/rewriter/public/critical_finder_support_util.h"
 #include "net/instaweb/rewriter/public/property_cache_util.h"
 #include "net/instaweb/rewriter/public/rewrite_driver.h"
@@ -26,6 +27,8 @@
 #include "net/instaweb/rewriter/public/rewrite_options.h"
 #include "net/instaweb/rewriter/public/server_context.h"
 #include "net/instaweb/util/public/fallback_property_page.h"
+#include "pagespeed/kernel/base/basictypes.h"
+#include "pagespeed/kernel/base/statistics.h"
 #include "pagespeed/kernel/base/string.h"
 #include "pagespeed/kernel/base/string_hash.h"
 #include "pagespeed/kernel/base/timer.h"
@@ -87,9 +90,18 @@ CriticalImagesFinder::Availability BeaconCriticalImagesFinder::Available(
 
 bool BeaconCriticalImagesFinder::ShouldBeacon(RewriteDriver* driver) {
   UpdateCriticalImagesSetInDriver(driver);
-  return ::net_instaweb::ShouldBeacon(
-      driver->critical_images_info()->proto.html_critical_image_support(),
-      *driver);
+  int64 next_beacon_timestamp_ms = 0;
+  CriticalImagesInfo* critical_images = driver->critical_images_info();
+  DCHECK(critical_images != NULL)
+      << "UpdateCriticalImagesSetInDriver must be called before ShouldBeacon";
+  if (critical_images != NULL) {
+    const CriticalImages& proto = critical_images->proto;
+    if (proto.has_html_critical_image_support()) {
+      next_beacon_timestamp_ms =
+          proto.html_critical_image_support().next_beacon_timestamp_ms();
+    }
+  }
+  return net_instaweb::ShouldBeacon(next_beacon_timestamp_ms, *driver);
 }
 
 BeaconMetadata BeaconCriticalImagesFinder::PrepareForBeaconInsertion(

net/instaweb/rewriter/critical_finder_support_util.cc

@@ -327,7 +327,7 @@ void WriteCriticalKeysToPropertyCache(
   }
 }
 
-bool ShouldBeacon(const CriticalKeys& proto, const RewriteDriver& driver) {
+bool ShouldBeacon(int64 next_beacon_timestamp_ms, const RewriteDriver& driver) {
   // When downstream cache integration is enabled, and there is a rebeaconing
   // key already specified in the config, we should only rebeacon when there
   // is a matching key in the beacon requesting header.
@@ -337,7 +337,7 @@ bool ShouldBeacon(const CriticalKeys& proto, const RewriteDriver& driver) {
         driver.request_headers()->Lookup1(kPsaShouldBeacon));
   }
   int64 now_ms = driver.timer()->NowMs();
-  return now_ms >= proto.next_beacon_timestamp_ms();
+  return now_ms >= next_beacon_timestamp_ms;
 }
 
 void PrepareForBeaconInsertionHelper(CriticalKeys* proto,
@@ -346,7 +346,8 @@ void PrepareForBeaconInsertionHelper(CriticalKeys* proto,
                                      bool using_candidate_key_detection,
                                      BeaconMetadata* result) {
   result->status = kDoNotBeacon;
-  if (!ShouldBeacon(*proto, *driver)) {
+  CHECK(proto);
+  if (!ShouldBeacon(proto->next_beacon_timestamp_ms(), *driver)) {
     return;
   }
 

net/instaweb/rewriter/public/critical_finder_support_util.h

@@ -108,7 +108,7 @@ void UpdateCriticalKeys(bool require_prior_support,
                         const StringSet& new_set, int support_value,
                         CriticalKeys* critical_keys);
 
-bool ShouldBeacon(const CriticalKeys& proto, const RewriteDriver& driver);
+bool ShouldBeacon(int64 next_beacon_timestamp_ms, const RewriteDriver& driver);
 
 enum CriticalKeysWriteFlags {
   kNoRequirementsOnPriorResult = 0,  // Nice name for lack of next two flags.