Adds an observer for the request coordinator.

components/offline_pages/background/request_coordinator.h

Index: components/offline_pages/background/request_coordinator.h
diff --git a/components/offline_pages/background/request_coordinator.h b/components/offline_pages/background/request_coordinator.h
index 3e52021e3597ca352a12cc6d2fdacad9c25b6db8..ad05ec8fece37dcd9fef6e2aa3e8ab95835ceb0a 100644
--- a/components/offline_pages/background/request_coordinator.h
+++ b/components/offline_pages/background/request_coordinator.h
@@ -10,6 +10,7 @@
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
 #include "components/keyed_service/core/keyed_service.h"
@@ -33,6 +34,30 @@ class Scheduler;
 // Coordinates queueing and processing save page later requests.
 class RequestCoordinator : public KeyedService {
  public:
+  // Status to return for failed notifications.
+  enum class SavePageStatus {
+    SUCCESS,
+    PRERENDER_FAILURE,
+    FOREGROUND_CANCELED,
+    SAVE_FAILED,
+    EXPIRED,
+    RETRY_COUNT_EXCEEDED,
+  };
+
+  // Nested observer class.  To make sure that no events are missed, the client
+  // code should first register for notifications, then GetAllRequests, and
+  // ignore all events before the return from GetAllRequests, and consume events
+  // after the return callback from GetAlLRequests.

[fgorski, 2016/08/11 17:03:58]

AlL -> All

nit: I believe we use |GetAllRequests| to distinguish methods, if nothing
changed.

[Pete Williamson, 2016/08/13 03:20:34]

Done.

+  class Observer {
+   public:
+    virtual void OnAdded(const SavePageRequest& request) = 0;
+    virtual void OnSucceeded(const SavePageRequest& request,
+                             int64_t offline_id) = 0;

[Dmitry Titov, 2016/08/11 03:41:55]

Once we agreed the id is inherited from request to the page, we don't seem to
need offline_id here.
I would remove it now since you will start inheriting id very soon and it'll be
nice to avoid new code written against this API to only have to change later.

[Pete Williamson, 2016/08/13 03:20:34]

Done.

+    virtual void OnFailed(const SavePageRequest& request,
+                          SavePageStatus status) = 0;
+    virtual void OnChanged(const SavePageRequest& request) = 0;
+  };
+
   // Callback to report when the processing of a triggered task is complete.
   typedef base::Callback<void(const SavePageRequest& request)>
       RequestPickedCallback;
@@ -93,6 +118,14 @@ class RequestCoordinator : public KeyedService {
     scheduler_callback_ = callback;
   }
 
+  // Observers implementing the RequestCoordinator::Observer interface can
+  // register here to get notifications of changes to request state.  This
+  // pointer is not owned, and it is the callers responsibility to remove the
+  // observer before the observer is deleted.
+  void AddObserver(RequestCoordinator::Observer* observer);
+
+  void RemoveObserver(RequestCoordinator::Observer* observer);
+
   // Returns the request queue used for requests.  Coordinator keeps ownership.
   RequestQueue* queue() { return queue_.get(); }
 
@@ -134,7 +167,12 @@ class RequestCoordinator : public KeyedService {
   void UpdateRequestCallback(const ClientId& client_id,
                              RequestQueue::UpdateRequestResult result);
 
-  void UpdateMultipleRequestCallback(RequestQueue::UpdateRequestResult result);
+  void UpdateMultipleRequestCallback(const std::vector<int64_t>& request_ids,
+                                     RequestQueue::UpdateRequestResult result);
+
+  void NotifyChangedListCallback(const std::vector<int64_t>& request_ids,
+                                 RequestQueue::GetRequestsResult result,
+                                 const std::vector<SavePageRequest>& requests);
 
   // Callback from the request picker when it has chosen our next request.
   void RequestPicked(const SavePageRequest& request);
@@ -151,6 +189,14 @@ class RequestCoordinator : public KeyedService {
 
   void TryNextRequest();
 
+  void NotifyAdded(const SavePageRequest& request);
+  void NotifySucceeded(const SavePageRequest& request, int64_t offline_id);
+  void NotifyFailed(const SavePageRequest& request, SavePageStatus status);
+  void NotifyChanged(const SavePageRequest& request);
+
+  // Sends a changed notification for each request_id in the list.
+  void SendNotifyChangeForRequestIdList(std::vector<int64_t> request_ids);
+
   // Returns the appropriate offliner to use, getting a new one from the factory
   // if needed.
   void GetOffliner();
@@ -174,6 +220,8 @@ class RequestCoordinator : public KeyedService {
   // Unowned pointer to the current offliner, if any.
   Offliner* offliner_;
   base::Time operation_start_time_;
+  // The observers.
+  base::ObserverList<Observer> observers_;
   // Last known conditions for network, battery
   std::unique_ptr<DeviceConditions> current_conditions_;
   // RequestCoordinator takes over ownership of the policy