Support sharing of ContentMain and BrowserMain code with embedded use cases (try #3).

content/public/browser/browser_main_parts.h

Index: content/public/browser/browser_main_parts.h
===================================================================
--- content/public/browser/browser_main_parts.h	(revision 121246)
+++ content/public/browser/browser_main_parts.h	(working copy)
@@ -10,6 +10,8 @@
 #include "content/common/content_export.h"
 #include "content/public/browser/browser_thread.h"
 
+class MessageLoop;
+
 namespace content {
 
 // This class contains different "stages" to be executed by |BrowserMain()|,
@@ -60,6 +62,10 @@
 
   virtual void PreMainMessageLoopStart() = 0;
 
+  // Return the main message loop object or NULL to use the default message
+  // loop object.
+  virtual MessageLoop* GetMainMessageLoop() = 0;
+
   virtual void PostMainMessageLoopStart() = 0;
 
   // Allows an embedder to do any extra toolkit initialization.