Don't abort drags if drag image generation fails.

Source/core/page/DragController.cpp

 /*
  * Copyright (C) 2007, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 913 matching lines @@
                 src->selection().setSelection(VisibleSelection::selectionFromContentsOfNode(node));
         }
 
         if (!dragImage) {
             ASSERT(src->page());
             float deviceScaleFactor = src->page()->deviceScaleFactor();
             dragImage = dragImageForLink(linkURL, hitTestResult.textContent(), deviceScaleFactor, mouseDraggedPoint, dragLocation);
         }
         doSystemDrag(dragImage.get(), dragLocation, mouseDraggedPoint, dataTransfer, src, true);
     } else if (state.m_dragType == DragSourceActionDHTML) {
-        if (!dragImage)
-            return false;
         doSystemDrag(dragImage.get(), dragLocation, dragOrigin, dataTransfer, src, false);
     } else {
         ASSERT_NOT_REACHED();
         return false;
     }
 
     return true;
 }
 
 void DragController::doSystemDrag(DragImage* image, const IntPoint& dragLocation, const IntPoint& eventPos, DataTransfer* dataTransfer, LocalFrame* frame, bool forLink)
@@ skipping 40 matching lines @@
 
 void DragController::trace(Visitor* visitor)
 {
     visitor->trace(m_page);
     visitor->trace(m_documentUnderMouse);
     visitor->trace(m_dragInitiator);
     visitor->trace(m_fileInputElementUnderMouse);
 }
 
 } // namespace blink