Add console warning for canceling uncancelable TouchEvent

Source/core/events/TouchEvent.cpp

 /*
  * Copyright 2008, The Android Open Source Project
  * Copyright (C) 2012 Research In Motion Limited. 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 copyright
@@ skipping 11 matching lines @@
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 
 #include "core/events/TouchEvent.h"
 
 #include "core/events/EventDispatcher.h"
+#include "core/frame/FrameConsole.h"
+#include "core/frame/LocalFrame.h"
 
 namespace WebCore {
 
 TouchEvent::TouchEvent()
 {
     ScriptWrappable::init(this);
 }
 
 TouchEvent::TouchEvent(TouchList* touches, TouchList* targetTouches,
         TouchList* changedTouches, const AtomicString& type,
@@ skipping 42 matching lines @@
 const AtomicString& TouchEvent::interfaceName() const
 {
     return EventNames::TouchEvent;
 }
 
 bool TouchEvent::isTouchEvent() const
 {
     return true;
 }
 
+void TouchEvent::preventDefault()
+{
+    MouseRelatedEvent::preventDefault();
+
+    // A common developer error is to wait too long before attempting to stop
+    // scrolling by consuming a touchmove event. Generate a warning if this
+    // event is uncancelable.
+    if (!cancelable() && view() && view()->frame()) {
+        view()->frame()->console().addMessage(JSMessageSource, WarningMessageLevel,
+            "Ignored attempt to cancel a " + type() + " event with cancelable=false, for example because scrolling is in progress and cannot be interrupted.");
+    }
+}
 void TouchEvent::trace(Visitor* visitor)
 {
     visitor->trace(m_touches);
     visitor->trace(m_targetTouches);
     visitor->trace(m_changedTouches);
     MouseRelatedEvent::trace(visitor);
 }
 
 PassRefPtr<TouchEventDispatchMediator> TouchEventDispatchMediator::create(PassRefPtrWillBeRawPtr<TouchEvent> touchEvent)
 {
@@ skipping 10 matching lines @@
     return toTouchEvent(EventDispatchMediator::event());
 }
 
 bool TouchEventDispatchMediator::dispatchEvent(EventDispatcher* dispatcher) const
 {
     event()->eventPath().adjustForTouchEvent(dispatcher->node(), *event());
     return dispatcher->dispatch();
 }
 
 } // namespace WebCore