Don't crash if there is no local main frame on WebView::handleInputEvent

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 2061 matching lines @@
         return EventTypeNames::touchend;
     case WebInputEvent::TouchCancel:
         return EventTypeNames::touchcancel;
     default:
         return String("unknown");
     }
 }
 
 bool WebViewImpl::handleInputEvent(const WebInputEvent& inputEvent)
 {
-    WebAutofillClient* autofillClient = mainFrameImpl() ? mainFrameImpl()->autofillClient() : 0;
+    // TODO(dcheng): The fact that this is getting called when there is no local
+    // main frame is problematic and probably indicates a bug in the input event
+    // routing code.
+    if (!mainFrameImpl())
+        return false;
+
+    WebAutofillClient* autofillClient = mainFrameImpl()->autofillClient();
     UserGestureNotifier notifier(autofillClient, &m_userGestureObserved);
     // On the first input event since page load, |notifier| instructs the
     // autofill client to unblock values of password input fields of any forms
     // on the page. There is a single input event, GestureTap, which can both
     // be the first event after page load, and cause a form submission. In that
     // case, the form submission happens before the autofill client is told
     // to unblock the password values, and so the password values are not
     // submitted. To avoid that, GestureTap is handled explicitly:
     if (inputEvent.type == WebInputEvent::GestureTap && autofillClient) {
         m_userGestureObserved = true;
@@ skipping 2407 matching lines @@
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 void WebViewImpl::forceNextWebGLContextCreationToFail()
 {
     WebGLRenderingContext::forceNextWebGLContextCreationToFail();
 }
 
 } // namespace blink