Don't stop and restart GCM when extension/app is being updated

chrome/browser/extensions/extension_gcm_app_handler.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/extensions/extension_gcm_app_handler.h"
 
 #include "base/bind.h"
 #include "base/lazy_instance.h"
 #include "base/location.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/services/gcm/gcm_profile_service.h"
 #include "chrome/browser/services/gcm/gcm_profile_service_factory.h"
 #include "components/gcm_driver/gcm_driver.h"
 #include "extensions/browser/extension_registry.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/permissions/permissions_data.h"
 
 #if !defined(OS_ANDROID)
 #include "chrome/browser/extensions/api/gcm/gcm_api.h"
 #endif
 
 namespace extensions {
 
 namespace {
 
+const char kDummyAppId[] = "extension.guard.dummy.id";
+
 base::LazyInstance<BrowserContextKeyedAPIFactory<ExtensionGCMAppHandler> >
     g_factory = LAZY_INSTANCE_INITIALIZER;
 
 bool IsGCMPermissionEnabled(const Extension* extension) {
   return extension->permissions_data()->HasAPIPermission(APIPermission::kGcm);
 }
 
 }  // namespace
 
 
@@ skipping 49 matching lines @@
     const gcm::GCMClient::SendErrorDetails& send_error_details) {
 #if !defined(OS_ANDROID)
   js_event_router_->OnSendError(app_id, send_error_details);
 #endif
 }
 
 void ExtensionGCMAppHandler::OnExtensionLoaded(
     content::BrowserContext* browser_context,
     const Extension* extension) {
   if (IsGCMPermissionEnabled(extension))
-    GetGCMDriver()->AddAppHandler(extension->id(), this);
+    AddAppHandler(extension->id());
 }
 
 void ExtensionGCMAppHandler::OnExtensionUnloaded(
     content::BrowserContext* browser_context,
     const Extension* extension,
     UnloadedExtensionInfo::Reason reason) {
-  if (IsGCMPermissionEnabled(extension))
-    GetGCMDriver()->RemoveAppHandler(extension->id());
+  if (!IsGCMPermissionEnabled(extension))
+    return;
+
+  if (reason == UnloadedExtensionInfo::REASON_UPDATE &&
+      GetGCMDriver()->app_handlers().size() == 1) {
+    // When the extension is being updated, it will be first unloaded and then
+    // loaded again by ExtensionService::AddExtension. If the app handler for
+    // this extension is the only handler, removing it and adding it again will
+    // cause the GCM service being stopped and restarted unnecessarily. To work
+    // around this, we add a dummy app handler to guard against it. This dummy
+    // app handler will be removed once the extension loading logic is done.
+    //
+    // Also note that the GCM message routing will not be interruptted during
+    // the update process since unloading and reloading extension are done in
+    // the single function ExtensionService::AddExtension.
+    AddDummyAppHandler();
+
+    base::MessageLoop::current()->PostTask(
+        FROM_HERE,
+        base::Bind(&ExtensionGCMAppHandler::RemoveDummyAppHandler,
+                   weak_factory_.GetWeakPtr()));
+  }
+
+  RemoveAppHandler(extension->id());
 }
 
 void ExtensionGCMAppHandler::OnExtensionUninstalled(
     content::BrowserContext* browser_context,
     const Extension* extension) {
   if (IsGCMPermissionEnabled(extension)) {
     GetGCMDriver()->Unregister(
         extension->id(),
         base::Bind(&ExtensionGCMAppHandler::OnUnregisterCompleted,
                    weak_factory_.GetWeakPtr(),
                    extension->id()));
-    GetGCMDriver()->RemoveAppHandler(extension->id());
+    RemoveAppHandler(extension->id());
   }
 }
 
+void ExtensionGCMAppHandler::AddDummyAppHandler() {
+  AddAppHandler(kDummyAppId);
+}
+
+void ExtensionGCMAppHandler::RemoveDummyAppHandler() {
+  RemoveAppHandler(kDummyAppId);
+}
+
 gcm::GCMDriver* ExtensionGCMAppHandler::GetGCMDriver() const {
   return gcm::GCMProfileServiceFactory::GetForProfile(profile_)->driver();
 }
 
 void ExtensionGCMAppHandler::OnUnregisterCompleted(
     const std::string& app_id, gcm::GCMClient::Result result) {
   // Nothing to do.
 }
 
+void ExtensionGCMAppHandler::AddAppHandler(const std::string& app_id) {
+  GetGCMDriver()->AddAppHandler(app_id, this);
+}
+
+void ExtensionGCMAppHandler::RemoveAppHandler(const std::string& app_id) {
+  GetGCMDriver()->RemoveAppHandler(app_id);
+}
+
 }  // namespace extensions