Catch uncaught promise rejections from V8 and log to console.

Source/web/WebKit.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 60 matching lines @@
 class EndOfTaskRunner : public WebThread::TaskObserver {
 public:
     virtual void willProcessTask() OVERRIDE
     {
         AnimationClock::notifyTaskStart();
     }
     virtual void didProcessTask() OVERRIDE
     {
         Microtask::performCheckpoint();
         V8GCController::reportDOMMemoryUsageToV8(mainThreadIsolate());
+        V8Initializer::reportRejectedPromises();
     }
 };
 
 } // namespace
 
 static WebThread::TaskObserver* s_endOfTaskRunner = 0;
 static WebThread::TaskObserver* s_pendingGCRunner = 0;
 static ThreadState::Interruptor* s_messageLoopInterruptor = 0;
 static ThreadState::Interruptor* s_isolateInterruptor = 0;
 
@@ skipping 163 matching lines @@
         channel->state = WTFLogChannelOn;
 #endif // !LOG_DISABLED
 }
 
 void resetPluginCache(bool reloadPages)
 {
     Page::refreshPlugins(reloadPages);
 }
 
 } // namespace blink