Add Observer in FaviconTabHelper

chrome/browser/favicon/favicon_tab_helper.h

Index: chrome/browser/favicon/favicon_tab_helper.h
diff --git a/chrome/browser/favicon/favicon_tab_helper.h b/chrome/browser/favicon/favicon_tab_helper.h
index 4a4aa1babcfebc3ea397708c18042f7aee172866..017bbb91b472f8e696c0c2ab24300878c8dd40d0 100644
--- a/chrome/browser/favicon/favicon_tab_helper.h
+++ b/chrome/browser/favicon/favicon_tab_helper.h
@@ -9,6 +9,7 @@
 
 #include "base/basictypes.h"
 #include "base/callback.h"
+#include "base/observer_list.h"
 #include "components/favicon/core/browser/favicon_client.h"
 #include "components/favicon/core/favicon_driver.h"
 #include "content/public/browser/web_contents_observer.h"
@@ -38,6 +39,13 @@ class FaviconTabHelper : public content::WebContentsObserver,
                          public FaviconDriver,
                          public content::WebContentsUserData<FaviconTabHelper> {
  public:
+  class Observer {
+   public:
+    // Called when favicon |image| is retrieved from either web site or history
+    // backend.
+    virtual void OnFaviconAvailable(const gfx::Image& image) = 0;
+  };
+
   ~FaviconTabHelper() override;
 
   // Initiates loading the favicon for the specified url.
@@ -70,6 +78,9 @@ class FaviconTabHelper : public content::WebContentsObserver,
   // Saves the favicon for the current page.
   void SaveFavicon();
 
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
   // FaviconDriver methods.
   int StartDownload(const GURL& url, int max_bitmap_size) override;
   void NotifyFaviconUpdated(bool icon_url_changed) override;
@@ -81,6 +92,7 @@ class FaviconTabHelper : public content::WebContentsObserver,
   void SetActiveFaviconImage(gfx::Image image) override;
   void SetActiveFaviconURL(GURL url) override;
   void SetActiveFaviconValidity(bool validity) override;
+  void OnFaviconAvailable(const gfx::Image& image) override;
 
   // Favicon download callback.
   void DidDownloadFavicon(
@@ -117,6 +129,8 @@ class FaviconTabHelper : public content::WebContentsObserver,
   // browser_defaults::kEnableTouchIcon is false.
   scoped_ptr<FaviconHandler> touch_icon_handler_;
 
+  ObserverList<Observer> observer_list_;
+
   DISALLOW_COPY_AND_ASSIGN(FaviconTabHelper);
 };