Clean up dependencies for disk_cache histogram_macros.h.

net/disk_cache/rankings.cc

 // Copyright (c) 2012 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/rankings.h"
 
 #include "base/metrics/histogram.h"
 #include "net/disk_cache/backend_impl.h"
 #include "net/disk_cache/disk_format.h"
 #include "net/disk_cache/entry_impl.h"
 #include "net/disk_cache/errors.h"
 #include "net/disk_cache/histogram_macros.h"
 #include "net/disk_cache/stress_support.h"
 
+// Provide a BackendImpl object to macros from histogram_macros.h.
+#define CACHE_UMA_BACKEND_IMPL_OBJ backend_
+
 using base::Time;
 using base::TimeTicks;
 
 namespace disk_cache {
 // This is used by crash_cache.exe to generate unit test files.
 NET_EXPORT_PRIVATE RankCrashes g_rankings_crash = NO_CRASH;
 }
 
 namespace {
 
@@ skipping 888 matching lines @@
 void Rankings::DecrementCounter(List list) {
   if (!count_lists_)
     return;
 
   DCHECK(control_data_->sizes[list] > 0);
   if (control_data_->sizes[list] > 0)
     control_data_->sizes[list]--;
 }
 
 }  // namespace disk_cache