Make app_custom_bindings.js lazily evaluated so it doesn't execute on every page load.

chrome/renderer/extensions/extension_dispatcher.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_RENDERER_EXTENSIONS_EXTENSION_DISPATCHER_H_
 #define CHROME_RENDERER_EXTENSIONS_EXTENSION_DISPATCHER_H_
 #pragma once
 
 #include <set>
 #include <string>
@@ skipping 86 matching lines @@
   }
   bool IsAdblockPlusWithWebRequestInstalled() const {
     return webrequest_adblock_plus_;
   }
   bool IsOtherExtensionWithWebRequestInstalled() const {
     return webrequest_other_;
   }
 
  private:
   friend class RenderViewTest;
+  typedef void (*BindingInstaller)(ModuleSystem* module_system,
+                                  v8::Handle<v8::Object> chrome,
+                                  v8::Handle<v8::Object> chrome_hidden);
 
   // RenderProcessObserver implementation:
   virtual bool OnControlMessageReceived(const IPC::Message& message) OVERRIDE;
   virtual void WebKitInitialized() OVERRIDE;
   virtual void IdleNotification() OVERRIDE;
 
   void OnMessageInvoke(const std::string& extension_id,
                        const std::string& function_name,
                        const base::ListValue& args,
                        const GURL& event_url,
@@ skipping 32 matching lines @@
   void UpdateOriginPermissions(UpdatedExtensionPermissionsInfo::Reason reason,
                                const Extension* extension,
                                const URLPatternSet& origins);
 
   void RegisterNativeHandlers(ModuleSystem* module_system,
                               ChromeV8Context* context);
 
   // Inserts static source code into |source_map_|.
   void PopulateSourceMap();
 
+  // Inserts BindingInstallers into |lazy_bindings_map_|.
+  void PopulateLazyBindingsMap();
+
+  // Sets up the bindings for the given api.
+  void InstallBindings(ModuleSystem* module_system,
+                       v8::Handle<v8::Context> v8_context,
+                       const std::string& api);
+
   // Returns the Feature::Context type of context for a JavaScript context.
   extensions::Feature::Context ClassifyJavaScriptContext(
       const std::string& extension_id,
       int extension_group,
       const ExtensionURLInfo& url_info);
 
   // True if this renderer is running extensions.
   bool is_extension_process_;
 
   // Contains all loaded extensions.  This is essentially the renderer
@@ skipping 29 matching lines @@
   // TODO(mpcomplete): remove. http://crbug.com/100411
   bool webrequest_adblock_;
   bool webrequest_adblock_plus_;
   bool webrequest_other_;
 
   ResourceBundleSourceMap source_map_;
 
   // Cache for the v8 representation of extension API schemas.
   extensions::V8SchemaRegistry v8_schema_registry_;
 
+  // Bindings that are defined lazily and have BindingInstallers to install
+  // them.
+  std::map<std::string, BindingInstaller> lazy_bindings_map_;
+
   DISALLOW_COPY_AND_ASSIGN(ExtensionDispatcher);
 };
 
 #endif  // CHROME_RENDERER_EXTENSIONS_EXTENSION_DISPATCHER_H_