Reland: Add GCMChannelStatusSyncer to schedule requests and enable/disable GCM

components/gcm_driver/gcm_driver_desktop.h

Index: components/gcm_driver/gcm_driver_desktop.h
diff --git a/components/gcm_driver/gcm_driver_desktop.h b/components/gcm_driver/gcm_driver_desktop.h
index 3199a48ae46903e68434b441a7e80a0ba0503519..a0659a7c4cf07e5f6839de52771c6cf49d8d2636 100644
--- a/components/gcm_driver/gcm_driver_desktop.h
+++ b/components/gcm_driver/gcm_driver_desktop.h
@@ -15,10 +15,13 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
+#include "components/gcm_driver/gcm_channel_status_syncer.h"
 #include "components/gcm_driver/gcm_client.h"
 #include "components/gcm_driver/gcm_connection_observer.h"
 #include "components/gcm_driver/gcm_driver.h"
 
+class PrefService;
+
 namespace base {
 class FilePath;
 class SequencedTaskRunner;
@@ -44,6 +47,7 @@ class GCMDriverDesktop : public GCMDriver {
   GCMDriverDesktop(
       scoped_ptr<GCMClientFactory> gcm_client_factory,
       const GCMClient::ChromeBuildInfo& chrome_build_info,
+      PrefService* prefs,
       const base::FilePath& store_path,
       const scoped_refptr<net::URLRequestContextGetter>& request_context,
       const scoped_refptr<base::SequencedTaskRunner>& ui_thread,
@@ -83,6 +87,12 @@ class GCMDriverDesktop : public GCMDriver {
   void SetAccountsForCheckin(
       const std::map<std::string, std::string>& account_tokens);
 
+  // Exposed for testing purpose.
+  bool gcm_enabled() const { return gcm_enabled_; }
+  GCMChannelStatusSyncer* gcm_channel_status_syncer_for_testing() {
+    return &gcm_channel_status_syncer_;
+  }
+
  protected:
   // GCMDriver implementation:
   virtual GCMClient::Result EnsureStarted() OVERRIDE;
@@ -124,6 +134,8 @@ class GCMDriverDesktop : public GCMDriver {
 
   void GetGCMStatisticsFinished(const GCMClient::GCMStatistics& stats);
 
+  GCMChannelStatusSyncer gcm_channel_status_syncer_;
+
   // Flag to indicate whether the user is signed in to a GAIA account.
   // TODO(jianli): To be removed when sign-in enforcement is dropped.
   bool signed_in_;
@@ -132,6 +144,7 @@ class GCMDriverDesktop : public GCMDriver {
   bool gcm_started_;
 
   // Flag to indicate if GCM is enabled.
+  // TODO(jianli): Removed when we switch completely to support all users.
   bool gcm_enabled_;
 
   // Flag to indicate the last known state of the GCM client. Because this