Adds an observer for the request coordinator.

components/offline_pages/background/request_queue_in_memory_store.h

Index: components/offline_pages/background/request_queue_in_memory_store.h
diff --git a/components/offline_pages/background/request_queue_in_memory_store.h b/components/offline_pages/background/request_queue_in_memory_store.h
index efab139785b10dd8cd9bd8a43856cd75a1e9f88a..22bae128f61efada534e1f8493b286ae01ee7f74 100644
--- a/components/offline_pages/background/request_queue_in_memory_store.h
+++ b/components/offline_pages/background/request_queue_in_memory_store.h
@@ -26,15 +26,18 @@ class RequestQueueInMemoryStore : public RequestQueueStore {
   void AddOrUpdateRequest(const SavePageRequest& request,
                           const UpdateCallback& callback) override;
 
-  // Remove requests by request ID.  In case the |request_ids| is empty, the
-  // result will be true, but the count of deleted pages will be 0.
+  // Remove requests by request ID. The callback will get a list of
+  // UpdateMultipleRequestResults and a list of the removed requests (for use by
+  // notifications).
   void RemoveRequests(const std::vector<int64_t>& request_ids,
                       const RemoveCallback& callback) override;
 
-  // Set the state of associated requests to |new_state|.
-  void ChangeRequestsState(const std::vector<int64_t>& request_ids,
-                           const SavePageRequest::RequestState new_state,
-                           const UpdateCallback& callback) override;
+  // Set the state of associated requests to |new_state|.  The callback will get
+  // a list of UpdateMultipleRequestResults, and a list of the updated requests.
+  void ChangeRequestsState(
+      const std::vector<int64_t>& request_ids,
+      const SavePageRequest::RequestState new_state,
+      const UpdateMultipleRequestsCallback& callback) override;
 
   void Reset(const ResetCallback& callback) override;