Disk Cache: Send only one eviction age data point per browser execution....

net/disk_cache/backend_impl.cc

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/disk_cache/backend_impl.h"
 
 #include "base/file_util.h"
 #include "base/histogram.h"
 #include "base/message_loop.h"
 #include "base/string_util.h"
@@ skipping 1057 matching lines @@
       }
     }
   }
 
   UMA_HISTOGRAM_TIMES(L"DiskCache.TotalTrimTime", Time::Now() - start);
   Trace("*** Trim Cache end ***");
   return;
 }
 
 void BackendImpl::ReportTrimTimes(EntryImpl* entry) {
-  std::wstring name(StringPrintf(L"DiskCache.TrimAge_%d",
-                                 data_->header.experiment));
-  static Histogram counter(name.c_str(), 1, 10000, 50);
-  counter.SetFlags(kUmaTargetedHistogramFlag);
-  counter.Add((Time::Now() - entry->GetLastUsed()).InHours());
+  static bool first_time = true;
+  if (first_time) {
+    first_time = false;
+    std::wstring name(StringPrintf(L"DiskCache.TrimAge_%d",
+                                   data_->header.experiment));
+    static Histogram counter(name.c_str(), 1, 10000, 50);
+    counter.SetFlags(kUmaTargetedHistogramFlag);
+    counter.Add((Time::Now() - entry->GetLastUsed()).InHours());
+  }
 }
 
 void BackendImpl::AddStorageSize(int32 bytes) {
   data_->header.num_bytes += bytes;
   DCHECK(data_->header.num_bytes >= 0);
 
   if (data_->header.num_bytes > max_size_)
     TrimCache(false);
 }
 
@@ skipping 111 matching lines @@
 
   return num_dirty;
 }
 
 bool BackendImpl::CheckEntry(EntryImpl* cache_entry) {
   RankingsNode* rankings = cache_entry->rankings()->Data();
   return !rankings->pointer;
 }
 
 }  // namespace disk_cache