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

public/web/WebFrameClient.h

Index: public/web/WebFrameClient.h
diff --git a/public/web/WebFrameClient.h b/public/web/WebFrameClient.h
index 2a06a4f73b1ac544c6a4328dd4e013b93b67db5d..6d0196a55473843fcde501eea35e49b40dff592d 100644
--- a/public/web/WebFrameClient.h
+++ b/public/web/WebFrameClient.h
@@ -262,6 +262,10 @@ public:
     // WARNING: This method may be called very frequently.
     virtual void didUpdateCurrentHistoryItem(WebLocalFrame*) { }
 
+    // The frame's manifest has changed.
+    virtual void didChangeManifest(WebLocalFrame*) { }
+
+
     // Misc ----------------------------------------------------------------
 
     // Called to retrieve the provider of desktop notifications.