Detect <link rel='manifest'> and notify embedder.

Source/web/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 788 matching lines @@
         return nullptr;
     return adoptPtr(m_webFrame->client()->createApplicationCacheHost(m_webFrame, client));
 }
 
 void FrameLoaderClientImpl::didStopAllLoaders()
 {
     if (m_webFrame->client())
         m_webFrame->client()->didAbortLoading(m_webFrame);
 }
 
+void FrameLoaderClientImpl::dispatchDidChangeManifest()
+{
+    if (m_webFrame->client())
+        m_webFrame->client()->didChangeManifest(m_webFrame);

[abarth-chromium, 2014/05/01 17:51:16]

Why not pass the manifest URL along in this notification?  I'd imagine the first
thing the embedder will do is query for the manifest URL.

Also, won't think notification fire even when the manifest hasn't changed?  For
example, if I have two manifest link elements, we'll fire this notification
twice even though the manifest only changed once (for the first element).

[mlamouri (slow - plz ping), 2014/05/01 18:00:09]

I tried to stay consistent with how icons update are propagated.
True. The chances that more than one manifest will be present are pretty low.
The cost of keeping track of the current manifest in Blink would be way higher.

+}
+
 } // namespace blink