Adds MessageLoopUIApplication for use on iOS.

base/run_loop.h

Index: base/run_loop.h
diff --git a/base/run_loop.h b/base/run_loop.h
index b85daf65aa13e9b7821a13ad6cda19a9bedd2fd5..831473714c74bb51afb573ead14df8850e140d07 100644
--- a/base/run_loop.h
+++ b/base/run_loop.h
@@ -15,6 +15,10 @@ namespace base {
 class MessagePumpForUI;
 #endif
 
+#if defined(OS_IOS)
+class MessagePumpUIApplication;
+#endif
+
 // Helper class to Run a nested MessageLoop. Please do not use nested
 // MessageLoops in production code! If you must, use this class instead of
 // calling MessageLoop::Run/Quit directly. RunLoop::Run can only be called once
@@ -76,6 +80,12 @@ class BASE_EXPORT RunLoop {
   friend class base::MessagePumpForUI;
 #endif
 
+#if defined(OS_IOS)
+  // iOS doesn't support the blocking MessageLoop::Run, so it calls
+  // BeforeRun directly.
+  friend class base::MessagePumpUIApplication;
+#endif
+
   // Return false to abort the Run.
   bool BeforeRun();
   void AfterRun();