Start and stop the GCM service on demand

chrome/browser/services/gcm/gcm_driver.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/services/gcm/gcm_driver.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 471 matching lines @@
 
    // Ensures that the GCM service is started when there is an interest.
   EnsureStarted();
 }
 
 void GCMDriver::RemoveAppHandler(const std::string& app_id) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   DCHECK(!app_id.empty());
 
   app_handlers_.erase(app_id);
+
+  // Stops the GCM service when no app intends to consume it.
+  if (app_handlers_.empty())
+    Stop();
 }
 
 void GCMDriver::Register(const std::string& app_id,
                          const std::vector<std::string>& sender_ids,
                          const RegisterCallback& callback) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   DCHECK(!app_id.empty());
   DCHECK(!sender_ids.empty());
   DCHECK(!callback.is_null());
 
@@ skipping 191 matching lines @@
 void GCMDriver::OnActiveAccountLogout() {
   CheckOut();
 }
 
 GCMClient::Result GCMDriver::EnsureStarted() {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 
   if (!gcm_enabled_)
     return GCMClient::GCM_DISABLED;
 
+  // Has any app requested the service?

[Nicolas Zea, 2014/05/22 17:06:31]

nit: has -> Have

[jianli, 2014/05/22 18:09:26]

Done.

+  if (app_handlers_.empty())
+    return GCMClient::UNKNOWN_ERROR;
+
   // Is the user signed in?
   const std::string account_id = identity_provider_->GetActiveAccountId();
   if (account_id.empty())
     return GCMClient::NOT_SIGNED_IN;
 
   // CheckIn could be called more than once when:
   // 1) The password changes.
   // 2) Register/send function calls it to ensure CheckIn is done.
   if (account_id_ == account_id)
     return GCMClient::SUCCESS;
@@ skipping 159 matching lines @@
     LOG(WARNING) << "request_gcm_statistics_callback_ is NULL.";
 }
 
 std::string GCMDriver::SignedInUserName() const {
   if (IsStarted())
     return identity_provider_->GetActiveUsername();
   return std::string();
 }
 
 }  // namespace gcm