Plumb an event through to content/ that is sent just before 'onload'.

Source/WebKit/chromium/src/FrameLoaderClientImpl.cpp

 /*
  * Copyright (C) 2009, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2011 Apple 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.
@@ skipping 465 matching lines @@
 {
     if (m_webFrame->client()) {
         WrappedResourceRequest webreq(request);
         WrappedResourceResponse webresp(response);
         m_webFrame->client()->didLoadResourceFromMemoryCache(
             m_webFrame, webreq, webresp);
     }
     return false;  // Do not suppress remaining notifications
 }
 
+void FrameLoaderClientImpl::dispatchWillHandleOnloadEvents()
+{
+    if (m_webFrame->client())
+        m_webFrame->client()->willHandleOnloadEvents(m_webFrame);
+}
+
 void FrameLoaderClientImpl::dispatchDidHandleOnloadEvents()
 {
     if (m_webFrame->client())
         m_webFrame->client()->didHandleOnloadEvents(m_webFrame);
 }
 
 // Redirect Tracking
 // =================
 // We want to keep track of the chain of redirects that occur during page
 // loading. There are two types of redirects, server redirects which are HTTP
@@ skipping 1192 matching lines @@
 }
 #endif
 
 void FrameLoaderClientImpl::dispatchWillInsertBody()
 {
     if (m_webFrame->client())
         m_webFrame->client()->willInsertBody(m_webFrame);
 }
 
 } // namespace WebKit