Push API: Fix unsubscribing from GCM on Android

components/gcm_driver/gcm_driver.h

Index: components/gcm_driver/gcm_driver.h
diff --git a/components/gcm_driver/gcm_driver.h b/components/gcm_driver/gcm_driver.h
index 04fb53660dbd7db2ec8ee9603c895b46c1baab50..fb20f3ac3af6435e31771301fcb296c98f15d9ce 100644
--- a/components/gcm_driver/gcm_driver.h
+++ b/components/gcm_driver/gcm_driver.h
@@ -37,8 +37,9 @@ class GCMDriver {
   GCMDriver();
   virtual ~GCMDriver();
 
-  // Registers |sender_id| for an app. A registration ID will be returned by
-  // the GCM server.
+  // Registers |sender_ids| for an app. A registration ID will be returned by
+  // the GCM server. On Android, only a single sender ID is supported, but
+  // instead multiple simultaneous registrations are allowed.
   // |app_id|: application ID.
   // |sender_ids|: list of IDs of the servers that are allowed to send the
   //               messages to the application. These IDs are assigned by the
@@ -48,12 +49,22 @@ class GCMDriver {
                 const std::vector<std::string>& sender_ids,
                 const RegisterCallback& callback);
 
-  // Unregisters an app from using GCM.
+  // Unregisters all sender_ids for an app. Only works on non-Android.
   // |app_id|: application ID.
   // |callback|: to be called once the asynchronous operation is done.
   void Unregister(const std::string& app_id,
                   const UnregisterCallback& callback);
 
+  // Unregisters an (app_id, sender_id) pair from using GCM. Only works on
+  // Android.
+  // TODO(jianli): Switch to using GCM's unsubscribe API.
+  // |app_id|: application ID.
+  // |sender_id|: the sender ID that was passed when registering.
+  // |callback|: to be called once the asynchronous operation is done.
+  void UnregisterWithSenderId(const std::string& app_id,
+                              const std::string& sender_id,
+                              const UnregisterCallback& callback);
+
   // Sends a message to a given receiver.
   // |app_id|: application ID.
   // |receiver_id|: registration ID of the receiver party.
@@ -146,6 +157,10 @@ class GCMDriver {
   // Platform-specific implementation of Unregister.
   virtual void UnregisterImpl(const std::string& app_id) = 0;
 
+  // Platform-specific implementation of UnregisterWithSenderId.
+  virtual void UnregisterWithSenderIdImpl(const std::string& app_id,
+                                          const std::string& sender_id);
+
   // Platform-specific implementation of Send.
   virtual void SendImpl(const std::string& app_id,
                         const std::string& receiver_id,
@@ -170,6 +185,11 @@ class GCMDriver {
   void ClearCallbacks();
 
  private:
+  // Common code shared by Unregister and UnregisterWithSenderId.
+  void UnregisterInternal(const std::string& app_id,
+                          const std::string* sender_id,
+                          const UnregisterCallback& callback);
+
   // Called after unregistration completes in order to trigger the pending
   // registration.
   void RegisterAfterUnregister(