Remove CACHE_STATISTICS preprocessor macro, assuming it's always 1.

It was added in 2012 and we decided that it's not required anymore.

pagespeed/system/system_cache_path.cc

@@ -131,13 +131,9 @@ SystemCachePath::SystemCachePath(const StringPiece& path,
     ThreadsafeCache* ts_cache =
         new ThreadsafeCache(lru_cache, factory->thread_system()->NewMutex());
     factory->TakeOwnership(ts_cache);
-#if CACHE_STATISTICS
     lru_cache_ = new CacheStats(kLruCache, ts_cache, factory->timer(),
                                 factory->statistics());
     factory->TakeOwnership(lru_cache_);
-#else
-    lru_cache_ = ts_cache;
-#endif
   }
 }
 

pagespeed/system/system_cache_path.h

@@ -151,11 +151,6 @@ class SystemCachePath {
   ServerContextSet server_context_set_ GUARDED_BY(mutex_);
 };
 
-// CACHE_STATISTICS is #ifdef'd to facilitate experiments with whether
-// tracking the detailed stats & histograms has a QPS impact.  Set it
-// to 0 to turn it off.
-#define CACHE_STATISTICS 1
-
 }  // namespace net_instaweb
 
 #endif  // PAGESPEED_SYSTEM_SYSTEM_CACHE_PATH_H_

pagespeed/system/system_caches.cc

@@ -186,13 +186,11 @@ SystemCaches::MemcachedInterfaces SystemCaches::GetMemcached(
 
     // Put the batcher above the stats so that the stats sees the MultiGets
     // and can show us the histogram of how they are sized.
-#if CACHE_STATISTICS
     memcached.async = new CacheStats(kMemcachedAsync,
                                      memcached.async,
                                      factory_->timer(),
                                      factory_->statistics());
     factory_->TakeOwnership(memcached.async);
-#endif
 
     CacheBatcher* batcher = new CacheBatcher(
         memcached.async, factory_->thread_system()->NewMutex(),
@@ -205,14 +203,10 @@ SystemCaches::MemcachedInterfaces SystemCaches::GetMemcached(
 
     // Populate the blocking memcached interface, giving it its own
     // statistics wrapper.
-#if CACHE_STATISTICS
     memcached.blocking = new CacheStats(kMemcachedBlocking, mem_cache,
                                         factory_->timer(),
                                         factory_->statistics());
     factory_->TakeOwnership(memcached.blocking);
-#else
-    memcached.blocking = mem_cache;
-#endif
   }
   return memcached;
 }