[Mac] Remove NSApplication from the renderer.

content/renderer/renderer_main.cc

Index: content/renderer/renderer_main.cc
diff --git a/content/renderer/renderer_main.cc b/content/renderer/renderer_main.cc
index 31b0781833079d476e37190e38ae867850a430ab..33aa0474134d62b48d285e7ffa9a604a4e32d5be 100644
--- a/content/renderer/renderer_main.cc
+++ b/content/renderer/renderer_main.cc
@@ -45,6 +45,7 @@
 
 #include "base/mac/mac_util.h"
 #include "base/mac/scoped_nsautorelease_pool.h"
+#include "base/message_loop/message_pump_mac.h"
 #include "third_party/WebKit/public/web/WebView.h"
 #endif  // OS_MACOSX
 
@@ -158,9 +159,11 @@ int RendererMain(const MainFunctionParams& parameters) {
 
   RendererMessageLoopObserver task_observer;
 #if defined(OS_MACOSX)
-  // As long as we use Cocoa in the renderer (for the forseeable future as of
-  // now; see http://crbug.com/306348 for info) we need to have a UI loop.
-  base::MessageLoopForUI main_message_loop;
+  // As long as scrollbars on Mac are painted with Cocoa, the message pump
+  // needs to be backed by a Foundation-level loop to process NSTimers. See
+  // http://crbug.com/306348#c24 for details.
+  scoped_ptr<base::MessagePump> pump(new base::MessagePumpNSRunLoop());
+  base::MessageLoop main_message_loop(pump.Pass());
 #else
   // The main message loop of the renderer services doesn't have IO or UI tasks.
   base::MessageLoop main_message_loop;