Trying changes to see the perfomance impact on Mac....

chrome/browser/browser_process.h

Index: chrome/browser/browser_process.h
===================================================================
--- chrome/browser/browser_process.h	(revision 76198)
+++ chrome/browser/browser_process.h	(working copy)
@@ -39,6 +39,7 @@
 class SidebarManager;
 class TabCloseableStateWatcher;
 class ThumbnailGenerator;
+class WatchDogThread;
 
 namespace base {
 class Thread;
@@ -115,6 +116,9 @@
   virtual base::Thread* background_x11_thread() = 0;
 #endif
 
+  // Returns the thread that is used for health check of all browser threads.
+  virtual WatchDogThread* watchdog_thread() = 0;
+
   virtual policy::BrowserPolicyConnector* browser_policy_connector() = 0;
 
   virtual IconManager* icon_manager() = 0;