Add BackgroundModeOptimizer that can restart the browser

chrome/browser/background/background_mode_manager.h

Index: chrome/browser/background/background_mode_manager.h
diff --git a/chrome/browser/background/background_mode_manager.h b/chrome/browser/background/background_mode_manager.h
index 986863df5d5bf078f00594fc4f26283e9cd4bbe3..3b857f87d9ef1c6f0fc9576373ebbf3a8c891656 100644
--- a/chrome/browser/background/background_mode_manager.h
+++ b/chrome/browser/background/background_mode_manager.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_BACKGROUND_BACKGROUND_MODE_MANAGER_H_
 
 #include <map>
+#include <memory>
 #include <set>
 #include <vector>
 
@@ -26,6 +27,7 @@
 #include "content/public/browser/notification_registrar.h"
 #include "extensions/common/extension.h"
 
+class BackgroundModeOptimizer;
 class BackgroundTrigger;
 class Browser;
 class PrefRegistrySimple;
@@ -87,6 +89,10 @@ class BackgroundModeManager
   // will not start it if it is not enabled.
   virtual void ResumeBackgroundMode();
 
+  // Invoked to take Chrome out of KeepAlive mode - chrome stops running in

[Bernhard Bauer, 2016/05/19 08:56:56]

Nit: capitalize "Chrome".

[dgn, 2016/06/20 17:45:18]

Done.

+  // the background and removes its status bar icon.
+  void EndBackgroundMode();

[sky, 2016/05/18 19:23:05]

Move implementation to match new position.

[dgn, 2016/06/20 17:45:18]

Made this private as it was before, introduced another method to replace it.

+
   // For testing purposes.
   int NumberOfBackgroundModeData();
 
@@ -310,10 +316,6 @@ class BackgroundModeManager
   // and has a status bar icon.
   void StartBackgroundMode();
 
-  // Invoked to take Chrome out of KeepAlive mode - chrome stops running in
-  // the background and removes its status bar icon.
-  void EndBackgroundMode();
-
   // Enables keep alive and the status tray icon if and only if background mode
   // is active and not suspended.
   virtual void UpdateKeepAliveAndTrayIcon();
@@ -427,6 +429,10 @@ class BackgroundModeManager
   // chrome would immediately exit due to having no open windows.
   std::unique_ptr<ScopedKeepAlive> keep_alive_for_startup_;
 
+  // Reference to the optimizer to use to reduce Chrome's footprint when in
+  // background mode. If null, optimizations are disabled.
+  std::unique_ptr<BackgroundModeOptimizer> optimizer_;
+
   // Set to true when Chrome is running with the --keep-alive-for-test flag
   // (used for testing background mode without having to install a background
   // app).