[Sync] Enable adding notifier observers from ProfileSyncService

chrome/browser/sync/glue/sync_backend_host.h

Index: chrome/browser/sync/glue/sync_backend_host.h
diff --git a/chrome/browser/sync/glue/sync_backend_host.h b/chrome/browser/sync/glue/sync_backend_host.h
index 0a6fde3d7581d1c55fce46f4bffab9c66bd98142..bafe1402f07628a69c6ba5e6ba88ab556163d912 100644
--- a/chrome/browser/sync/glue/sync_backend_host.h
+++ b/chrome/browser/sync/glue/sync_backend_host.h
@@ -27,6 +27,7 @@
 #include "sync/internal_api/public/util/unrecoverable_error_handler.h"
 #include "sync/internal_api/public/util/weak_handle.h"
 #include "sync/notifier/sync_notifier_factory.h"
+#include "sync/notifier/sync_notifier_observer.h"
 #include "sync/protocol/encryption.pb.h"
 #include "sync/protocol/sync_protocol_error.h"
 
@@ -51,7 +52,7 @@ class SyncPrefs;
 // activity.
 // NOTE: All methods will be invoked by a SyncBackendHost on the same thread
 // used to create that SyncBackendHost.
-class SyncFrontend {
+class SyncFrontend : public syncer::SyncNotifierObserver {
  public:
   SyncFrontend() {}
 
@@ -175,9 +176,13 @@ class SyncBackendHost : public BackendDataTypeConfigurer {
       syncer::ReportUnrecoverableErrorFunction
           report_unrecoverable_error_function);
 
-  // Called from |frontend_loop| to update SyncCredentials.
+  // Called on |frontend_loop| to update SyncCredentials.
   void UpdateCredentials(const syncer::SyncCredentials& credentials);
 
+  // Registers the underlying frontend for the given IDs to the
+  // underlying notifier.
+  void UpdateRegisteredInvalidationIds(const syncer::ObjectIdSet& ids);
+
   // This starts the SyncerThread running a Syncer object to communicate with
   // sync servers.  Until this is called, no changes will leave or enter this
   // browser from the cloud / sync servers.
@@ -349,6 +354,8 @@ class SyncBackendHost : public BackendDataTypeConfigurer {
       const syncer::WeakHandle<syncer::JsBackend>& js_backend, bool success,
       syncer::ModelTypeSet restored_types);
 
+  SyncFrontend* frontend() { return frontend_; }
+
  private:
   // The real guts of SyncBackendHost, to keep the public client API clean.
   class Core;
@@ -460,6 +467,14 @@ class SyncBackendHost : public BackendDataTypeConfigurer {
       const syncer::WeakHandle<syncer::JsBackend>& js_backend,
       syncer::ModelTypeSet failed_configuration_types);
 
+  // syncer::SyncNotifierObserver-like functions.
+  void HandleNotificationsEnabledOnFrontendLoop();
+  void HandleNotificationsDisabledOnFrontendLoop(
+      syncer::NotificationsDisabledReason reason);
+  void HandleIncomingNotificationOnFrontendLoop(
+      const syncer::ObjectIdPayloadMap& id_payloads,
+      syncer::IncomingNotificationSource source);
+
   // Must be called on |frontend_loop_|.  |done_callback| is called on
   // |frontend_loop_|.
   void RefreshNigori(const base::Closure& done_callback);