[Media Router] Set initial sink availability to available in MRMojoImpl.

chrome/browser/media/router/media_router_mojo_impl_unittest.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/run_loop.h"
@@ skipping 315 matching lines @@
   EXPECT_CALL(issue_observer2,
               OnIssueUpdated(Pointee(EqualsIssue(expected_issue2))));
   media_router_proxy_->OnIssue(mojo_issue2.Pass());
   ProcessEventLoop();
 
   issue_observer1.UnregisterObserver();
   issue_observer2.UnregisterObserver();
 }
 
 TEST_F(MediaRouterMojoImplTest, RegisterAndUnregisterMediaSinksObserver) {
+  router()->OnSinkAvailabilityUpdated(
+      interfaces::MediaRouter::SINK_AVAILABILITY_AVAILABLE);
   MediaSource media_source(kSource);
 
   MockMediaRouter mock_router;
   EXPECT_CALL(mock_media_route_provider_,
               StartObservingMediaSinks(mojo::String(kSource)))
       .Times(2);
   EXPECT_CALL(mock_media_route_provider_,
               StartObservingMediaSinks(mojo::String(kSource2)));
 
   MediaSinksObserver* captured_observer;
@@ skipping 600 matching lines @@
   EXPECT_CALL(provide_handler_, Invoke(testing::Not("")));
   EXPECT_CALL(*process_manager_, IsEventPageSuspended(kExtensionId))
       .WillOnce(Return(false));
   EXPECT_CALL(mock_media_route_provider_, CloseRoute(mojo::String(kRouteId2)))
       .Times(kMaxPendingRequests);
   RegisterMediaRouteProvider();
   ProcessEventLoop();
 }
 
 }  // namespace media_router