Add UMA stats for ExtensionCache

chrome/browser/extensions/updater/extension_cache_impl.cc

 // Copyright 2014 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 "chrome/browser/extensions/updater/extension_cache_impl.h"
 
 #include "base/bind.h"
 #include "base/memory/singleton.h"
+#include "base/metrics/histogram.h"
 #include "base/sequenced_task_runner.h"
 #include "base/stl_util.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/crx_installer.h"
 #include "chrome/browser/extensions/updater/local_extension_cache.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_source.h"
@@ skipping 78 matching lines @@
   else
     callback.Run(file_path, true);
 }
 
 void ExtensionCacheImpl::OnCacheInitialized() {
   for (std::vector<base::Closure>::iterator it = init_callbacks_.begin();
        it != init_callbacks_.end(); ++it) {
     it->Run();
   }
   init_callbacks_.clear();
+
+  uint64 cache_size = 0;
+  size_t extensions_count = 0;
+  if (cache_->GetStatistics(&cache_size, &extensions_count)) {
+    UMA_HISTOGRAM_COUNTS_100("Extensions.ExtensionCacheCount",
+                             extensions_count);
+    UMA_HISTOGRAM_MEMORY_MB("Extensions.ExtensionCacheSize",
+                            cache_size / (1024 * 1024));
+  }
 }
 
 void ExtensionCacheImpl::Observe(int type,
                                  const content::NotificationSource& source,
                                  const content::NotificationDetails& details) {
   if (!cache_)
     return;
 
   switch (type) {
     case chrome::NOTIFICATION_EXTENSION_INSTALL_ERROR: {
       extensions::CrxInstaller* installer =
           content::Source<extensions::CrxInstaller>(source).ptr();
       // TODO(dpolukhin): remove extension from cache only if installation
       // failed due to file corruption.
       cache_->RemoveExtension(installer->expected_id());
       break;
     }
 
     default:
       NOTREACHED();
   }
 }
 
 }  // namespace extensions