Only return the visible page actions from PageActionController.

chrome/browser/extensions/extension_tab_helper.h

Index: chrome/browser/extensions/extension_tab_helper.h
diff --git a/chrome/browser/extensions/extension_tab_helper.h b/chrome/browser/extensions/extension_tab_helper.h
index 16b4f5fcb391e9fe356ea6ada4ca0db3be3c0c53..7a5a4f65ffc38912b7f087f0b1d85af78ed28865 100644
--- a/chrome/browser/extensions/extension_tab_helper.h
+++ b/chrome/browser/extensions/extension_tab_helper.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
 #include "chrome/browser/extensions/app_notify_channel_setup.h"
 #include "chrome/browser/extensions/extension_function_dispatcher.h"
 #include "chrome/browser/extensions/image_loading_tracker.h"
@@ -33,6 +34,15 @@ class ExtensionTabHelper
       public AppNotifyChannelSetup::Delegate,
       public base::SupportsWeakPtr<ExtensionTabHelper> {
  public:
+  class Observer {
+   public:
+    // Called when the page action state (such as visibility, title) changes.
+    virtual void OnPageActionStateChanged() = 0;
+
+   protected:
+    virtual ~Observer() {}
+  };
+
   explicit ExtensionTabHelper(TabContentsWrapper* wrapper);
   virtual ~ExtensionTabHelper();
 
@@ -50,6 +60,10 @@ class ExtensionTabHelper
   // the data is available.
   void GetApplicationInfo(int32 page_id);
 
+  // Observer management.
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
   // App extensions ------------------------------------------------------------
 
   // Sets the extension denoting this as an app. If |extension| is non-null this
@@ -172,6 +186,8 @@ class ExtensionTabHelper
 
   TabContentsWrapper* wrapper_;
 
+  ObserverList<Observer> observers_;
+
   DISALLOW_COPY_AND_ASSIGN(ExtensionTabHelper);
 };