Add Observer in FaviconTabHelper

components/favicon/core/favicon_driver.h

Index: components/favicon/core/favicon_driver.h
diff --git a/components/favicon/core/favicon_driver.h b/components/favicon/core/favicon_driver.h
index dadd43c12e7be7ca93db8eac4d5bacc0ddd44b09..8fcbba6fef99b2d0da96405e7f09a4d3694c5c8b 100644
--- a/components/favicon/core/favicon_driver.h
+++ b/components/favicon/core/favicon_driver.h
@@ -61,6 +61,9 @@ class FaviconDriver {
   // Sets whether the page's favicon is valid (if false, the default favicon is
   // being used). Requires GetActiveURL() to be valid.
   virtual void SetActiveFaviconValidity(bool validity) = 0;
+
+  // Notifies the driver favicon |image| is available to use.
+  virtual void OnFaviconAvailable(const gfx::Image& image) = 0;

[sky, 2014/10/30 03:34:31]

Can we leave the FaviconHandler as it was, meaning calling into
SetActiveFaviconImage and instead make FaviconTabHelper take a boolean as to
whether it should push to NavigationEntry or not? In either can it notifies the
observer.

[michaelbai, 2014/10/30 19:22:50]

Let me know if you are happy with new patch.

 };
 
 #endif  // COMPONENTS_FAVICON_CORE_FAVICON_DRIVER_H_