Relanding "Add apk for running content_browsertests"

base/message_loop.h

Index: base/message_loop.h
diff --git a/base/message_loop.h b/base/message_loop.h
index 446a520d114b104dc1ad30a7e1aebb40c3ec9961..b690940b8c4abfd7e3375864a2e0d528e491eb53 100644
--- a/base/message_loop.h
+++ b/base/message_loop.h
@@ -120,9 +120,10 @@ class BASE_EXPORT MessageLoop : public base::MessagePump::Delegate {
   static void EnableHistogrammer(bool enable_histogrammer);
 
   typedef base::MessagePump* (MessagePumpFactory)();
-  // Using the given base::MessagePumpForUIFactory to override the default
-  // MessagePump implementation for 'TYPE_UI'.
-  static void InitMessagePumpForUIFactory(MessagePumpFactory* factory);
+  // Uses the given base::MessagePumpForUIFactory to override the default
+  // MessagePump implementation for 'TYPE_UI'. Returns true if the factory
+  // was successfully registered.
+  static bool InitMessagePumpForUIFactory(MessagePumpFactory* factory);
 
   // A DestructionObserver is notified when the current MessageLoop is being
   // destroyed.  These observers are notified prior to MessageLoop::current()