[Sync] InvalidationService shouldn't CHECK when registering ObjectId for more than one handler

components/invalidation/invalidator.h

Index: components/invalidation/invalidator.h
diff --git a/components/invalidation/invalidator.h b/components/invalidation/invalidator.h
index 35c81de0af4307c8101bdfa9ebeb45f773349a6e..fc869b14df141a35f76e5e027ce7c1e8c0897448 100644
--- a/components/invalidation/invalidator.h
+++ b/components/invalidation/invalidator.h
@@ -59,9 +59,10 @@ class INVALIDATION_EXPORT Invalidator {
 
   // Updates the set of ObjectIds associated with |handler|.  |handler| must
   // not be NULL, and must already be registered.  An ID must be registered for
-  // at most one handler.
-  virtual void UpdateRegisteredIds(InvalidationHandler* handler,
-                                   const ObjectIdSet& ids) = 0;
+  // at most one handler. If ID is already registered function returns false.
+  virtual bool UpdateRegisteredIds(InvalidationHandler* handler,
+                                   const ObjectIdSet& ids)
+      WARN_UNUSED_RESULT = 0;
 
   // Stops sending notifications to |handler|.  |handler| must not be NULL, and
   // it must already be registered.  Note that this doesn't unregister the IDs