[Media Session] Notify mojo observer from content

Notifies the mojo observer from content::MediaSessionImpl
when the supported actions change.

BUG=892771

Change-Id: Iea1edf130b415d44ab9f32f7b6506d53f4558280
Reviewed-on: https://chromium-review.googlesource.com/c/1379917Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619737}

content/browser/media/session/media_session_impl.cc

@@ -224,6 +224,13 @@ void MediaSessionImpl::NotifyMediaSessionActionsChange(
     const std::set<media_session::mojom::MediaSessionAction>& actions) {
   for (auto& observer : observers_)
     observer.MediaSessionActionsChanged(actions);
+
+  std::vector<media_session::mojom::MediaSessionAction> actions_vec(
+      actions.begin(), actions.end());
+  mojo_observers_.ForAllPtrs(
+      [&actions_vec](media_session::mojom::MediaSessionObserver* observer) {
+        observer->MediaSessionActionsChanged(actions_vec);
+      });
 }
 
 bool MediaSessionImpl::AddPlayer(MediaSessionPlayerObserver* observer,
@@ -754,6 +761,15 @@ void MediaSessionImpl::AddObserver(
   observer->MediaSessionMetadataChanged(
       routed_service_ ? routed_service_->metadata() : base::nullopt);
 
+  if (routed_service_) {
+    std::vector<media_session::mojom::MediaSessionAction> actions(
+        routed_service_->actions().begin(), routed_service_->actions().end());
+    observer->MediaSessionActionsChanged(actions);
+  } else {
+    observer->MediaSessionActionsChanged(
+        std::vector<media_session::mojom::MediaSessionAction>());
+  }
+
   mojo_observers_.AddPtr(std::move(observer));
 }
 

content/browser/media/session/media_session_impl_service_routing_unittest.cc

@@ -605,4 +605,27 @@ TEST_F(MediaSessionImplServiceRoutingTest,
   }
 }
 
+TEST_F(MediaSessionImplServiceRoutingTest,
+       NotifyMojoObserverWhenActionsChange) {
+  CreateServiceForFrame(main_frame_);
+  StartPlayerForFrame(main_frame_);
+
+  services_[main_frame_]->EnableAction(
+      media_session::mojom::MediaSessionAction::kPlay);
+
+  media_session::test::MockMediaSessionMojoObserver observer(
+      *GetMediaSession());
+  observer.WaitForActions();
+
+  EXPECT_EQ(1u, observer.actions().size());
+  EXPECT_EQ(media_session::mojom::MediaSessionAction::kPlay,
+            observer.actions()[0]);
+
+  services_[main_frame_]->DisableAction(
+      media_session::mojom::MediaSessionAction::kPlay);
+  observer.WaitForActions();
+
+  EXPECT_TRUE(observer.actions().empty());
+}
+
 }  // namespace content