Extensions: Send the tab id to platform apps.

chrome/renderer/extensions/media_galleries_custom_bindings.h

Index: chrome/renderer/extensions/media_galleries_custom_bindings.h
===================================================================
--- chrome/renderer/extensions/media_galleries_custom_bindings.h	(revision 246091)
+++ chrome/renderer/extensions/media_galleries_custom_bindings.h	(working copy)
@@ -12,10 +12,16 @@
 // Implements custom bindings for the media galleries API.
 class MediaGalleriesCustomBindings : public ChromeV8Extension {
  public:
+  static void PushSenderTabId(ChromeV8Context* context, int tab_id);
+  static void PopSenderTabId(ChromeV8Context* context);
+
   MediaGalleriesCustomBindings(Dispatcher* dispatcher,
                                ChromeV8Context* context);
 
  private:
+  void GetSenderTabId(ChromeV8Context* context,
+                      const v8::FunctionCallbackInfo<v8::Value>& args);
+
   DISALLOW_COPY_AND_ASSIGN(MediaGalleriesCustomBindings);
 };