Refactor Extension initialization logic. Add tracing and additional histogram.

chrome/browser/extensions/installed_loader.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_INSTALLED_LOADER_H_
 #define CHROME_BROWSER_EXTENSIONS_INSTALLED_LOADER_H_
 
 class ExtensionService;
 
 namespace extensions {
@@ skipping 12 matching lines @@
   void Load(const ExtensionInfo& info, bool write_to_prefs);
 
   // Loads all installed extensions (used by startup and testing code).
   void LoadAllExtensions();
 
  private:
   // Returns the flags that should be used with Extension::Create() for an
   // extension that is already installed.
   int GetCreationFlags(const ExtensionInfo* info);
 
+  // Store metrics related to the loaded extensions.

[Yoyo Zhou, 2015/02/25 00:19:58]

Store/Load seem like the wrong verbs here. How about RecordExtensionsMetrics?

[rkaplow, 2015/02/25 16:37:49]

sounds better.

+  void LoadExtensionsMetrics();
+
   ExtensionService* extension_service_;
   ExtensionRegistry* extension_registry_;
 
   ExtensionPrefs* extension_prefs_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_INSTALLED_LOADER_H_