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..0640aab0024e6e5132f4297dbe62931e18499c17 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 +34,19 @@ class Scheduler;
 // Coordinates queueing and processing save page later requests.
 class RequestCoordinator : public KeyedService {
  public:
+  // Nested observer class
+  class Observer {
+   public:
+    virtual void OnAdded(const SavePageRequest& request) = 0;
+    virtual void OnSucceeded(
+        const SavePageRequest& request, int64_t offline_id) = 0;

[fgorski, 2016/08/10 21:30:44]

We should discuss making offline_id == request_id.

[Pete Williamson, 2016/08/11 00:08:36]

TODO added (in the SavePageLater function)

+    // TODO(petewil): Consider what the type of faliure_code should be.  We
+    // could use a new enum, re-use the offliner status enum, or just an int.
+    virtual void OnFailed(
+        const SavePageRequest& request, int64_t failure_code) = 0;
+    virtual void OnChanged(const SavePageRequest& request) = 0;

[fgorski, 2016/08/10 21:30:44]

Did we consider OnUpdated?

[Pete Williamson, 2016/08/11 00:08:36]

We discussed this in person, and nobody had a strong preference.  Code Search
shows more instances of OnChanged than OnUpdated, so I think it is more common,
sticking with OnChanged for now.

+  };
+
   // Callback to report when the processing of a triggered task is complete.
   typedef base::Callback<void(const SavePageRequest& request)>
       RequestPickedCallback;
@@ -93,6 +107,17 @@ 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 unowned, and it is the callers responsibility to remove the

[fgorski, 2016/08/10 21:30:44]

nit: "not owned" sounds better here.

[Pete Williamson, 2016/08/11 00:08:36]

Done.

+  // observer before the observer is deleted.  Add events after attaching an
+  // observer will be reported, even if the listener has not called
+  // GetQueuedRequests yet, so before GetQueuedRequests is called, the listener

[fgorski, 2016/08/10 21:30:44]

I think I disagree with Dmitry about having this part of the comment. Let's
discuss it today.

[Pete Williamson, 2016/08/11 00:08:36]

Comment updated per our discussion, and moved to the observer instead of the
AddObserver method.

+  // may need to ignore events.
+  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(); }
 
@@ -136,6 +161,10 @@ class RequestCoordinator : public KeyedService {
 
   void UpdateMultipleRequestCallback(RequestQueue::UpdateRequestResult result);
 
+  void NotifyChangedListCallback(const std::vector<int64_t> request_ids,

[fgorski, 2016/08/10 21:30:44]

is copying intended here?

[Pete Williamson, 2016/08/11 00:08:36]

Done.

+                                 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 +180,14 @@ 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, int64_t failure_code);
+  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 +211,8 @@ 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