Add an explicit dispose step for WebDevToolsAgentImpl.

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 1658 matching lines @@
         m_devToolsAgent->willBeDestroyed();
 
     if (m_page) {
         // Initiate shutdown for the entire frameset.  This will cause a lot of
         // notifications to be sent.
         m_page->willBeDestroyed();
         m_page.clear();
     }
 
     // Should happen after m_page.clear().
-    if (m_devToolsAgent)
+    if (m_devToolsAgent) {
+        m_devToolsAgent->dispose();
         m_devToolsAgent.clear();
+    }
 
     // Reset the delegate to prevent notifications being sent as we're being
     // deleted.
     m_client = nullptr;
 
     deref();  // Balances ref() acquired in WebView::create
 }
 
 void WebViewImpl::willStartLiveResize()
 {
@@ skipping 2961 matching lines @@
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 void WebViewImpl::forceNextWebGLContextCreationToFail()
 {
     WebGLRenderingContext::forceNextWebGLContextCreationToFail();
 }
 
 } // namespace blink