[Media Router] Sync state when MR extension is (re)connected to MR.

chrome/browser/media/router/mojo/media_router_mojo_impl.h

Index: chrome/browser/media/router/mojo/media_router_mojo_impl.h
diff --git a/chrome/browser/media/router/mojo/media_router_mojo_impl.h b/chrome/browser/media/router/mojo/media_router_mojo_impl.h
index 8f311c9a84260ca91ba3c3d2472c90688953bbed..c91501c2affc7c36d3e5c805501cba53c63d6c55 100644
--- a/chrome/browser/media/router/mojo/media_router_mojo_impl.h
+++ b/chrome/browser/media/router/mojo/media_router_mojo_impl.h
@@ -165,6 +165,8 @@ class MediaRouterMojoImpl : public MediaRouterBase,
                            AttemptedWakeupTooManyTimes);
   FRIEND_TEST_ALL_PREFIXES(MediaRouterMojoExtensionTest,
                            WakeupFailedDrainsQueue);
+  FRIEND_TEST_ALL_PREFIXES(MediaRouterMojoExtensionTest,
+                           SyncStateToMediaRouteProvider);
 
   // The max number of pending requests allowed. When number of pending requests
   // exceeds this number, the oldest request will be dropped.
@@ -199,9 +201,6 @@ class MediaRouterMojoImpl : public MediaRouterBase,
     MediaRoutesQuery();
     ~MediaRoutesQuery();
 
-    // True if the query has been sent to the MRPM.  False otherwise.
-    bool is_active = false;
-
     // Cached list of routes and joinable route IDs for the query.
     base::Optional<std::vector<MediaRoute>> cached_route_list;
     std::vector<std::string> joinable_route_ids;
@@ -309,6 +308,17 @@ class MediaRouterMojoImpl : public MediaRouterBase,
   // Error handler callback for |binding_| and |media_route_provider_|.
   void OnConnectionError();
 
+  // Issues 0+ calls to |media_route_provider_| to ensure its state is in sync
+  // with MediaRouter on a best-effort basis. This method can be only called if
+  // |media_route_provider_| is a valid handle.

[mark a. foltz, 2017/05/03 17:37:08]

Logically, this should be kicked off in RegisterMediaRouteProvider().  Won't the
handle be guaranteed to be valid then?

[imcheng, 2017/05/03 18:22:41]

Correct. In other words, having a valid MRP handle is a precondition of this
method.

+  // The extension might have become out of sync with MediaRouter due to one
+  // of few reasons:
+  // (1) The extension crashed and lost unpersisted changes.
+  // (2) The extension was updated; temporary data is cleared.
+  // (3) The extension has an unforseen bug which causes temporary data to be
+  //     persisted incorrectly on suspension.
+  void EnsureMediaRouteProviderStateSynced();

[mark a. foltz, 2017/05/03 17:37:08]

Can this be a verb, i.e. SyncToMediaRouteProvider() ?

[imcheng, 2017/05/03 18:22:41]

Renamed to SyncStateToMediaRouteProvider.

+
   // mojom::MediaRouter implementation.
   void RegisterMediaRouteProvider(
       mojom::MediaRouteProviderPtr media_route_provider_ptr,