Protect WebViewImpl::handleGestureEvent from null client

Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 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 659 matching lines @@
         syntheticGestureEvent.data.scrollUpdate.inertial = true;
 
         if (m_page && m_page->mainFrame() && m_page->mainFrame()->isLocalFrame() && m_page->deprecatedLocalMainFrame()->view())
             return handleGestureEvent(syntheticGestureEvent);
     }
     return false;
 }
 
 bool WebViewImpl::handleGestureEvent(const WebGestureEvent& event)
 {
+    if (!m_client)
+        return false;
+
     bool eventSwallowed = false;
     bool eventCancelled = false; // for disambiguation
 
     // Special handling for slow-path fling gestures.
     switch (event.type) {
     case WebInputEvent::GestureFlingStart: {
         if (mainFrameImpl()->frame()->eventHandler().isScrollbarHandlingGestures())
             break;
         m_client->cancelScheduledContentIntents();
         m_positionOnFlingStart = WebPoint(event.x, event.y);
@@ skipping 3999 matching lines @@
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 void WebViewImpl::forceNextWebGLContextCreationToFail()
 {
     WebGLRenderingContext::forceNextWebGLContextCreationToFail();
 }
 
 } // namespace blink