getUserMedia: handle the device starting status report.

content/browser/renderer_host/media/video_capture_controller_unittest.cc

 // Copyright (c) 2012 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 "content/browser/renderer_host/media/video_capture_controller.h"
 
 #include <stdint.h>
 #include <string.h>
 
 #include <memory>
@@ skipping 785 matching lines @@
   // second frame. Since the new |device_client_| is still alive, the second
   // buffer is expected to stay alive.
   EXPECT_CALL(*client_a_, DoBufferDestroyed(_, first_buffer_id)).Times(0);
   EXPECT_CALL(*client_a_, DoBufferDestroyed(_, second_buffer_id)).Times(0);
   controller_->ReturnBuffer(arbitrary_route_id_, client_a_.get(),
                             second_buffer_id, arbitrary_utilization);
   base::RunLoop().RunUntilIdle();
   Mock::VerifyAndClearExpectations(client_a_.get());
 }
 
+// Because OnStarted event will be called only once from each device, it's the
+// job of VideoCaptureController to report OnStarted event to all the clients.

[chfremer, 2017/03/02 17:56:10]

I like the test!
For the description comment here I recommend using a sentence that starts with
"Tests that ...". 
The goal of the description comment is to allow the reader quickly understand
what the test does without having to read the actual code.

In this case "Tests that the VideoCaptureController reports OnStarted() to all
clients, even if they connect after VideoCaptureController::OnStarted() has been
invoked."

[braveyao, 2017/03/03 17:53:12]

Done.

+TEST_F(VideoCaptureControllerTest, OnStartedForMultipleClients) {
+  media::VideoCaptureParams session_100;
+  session_100.requested_format = media::VideoCaptureFormat(
+      gfx::Size(320, 240), 30, media::PIXEL_FORMAT_I420);
+  media::VideoCaptureParams session_200 = session_100;
+  media::VideoCaptureParams session_300 = session_100;
+
+  const VideoCaptureControllerID client_a_route_1(1);
+  const VideoCaptureControllerID client_a_route_2(2);
+  const VideoCaptureControllerID client_b_route_1(3);
+
+  controller_->AddClient(client_a_route_1, client_a_.get(), 100, session_100);
+  controller_->AddClient(client_b_route_1, client_b_.get(), 300, session_300);
+  ASSERT_EQ(2, controller_->GetClientCount());
+
+  {
+    InSequence s;
+    // Simulate the OnStarted event from device.
+    EXPECT_CALL(*client_a_, OnStarted(_));
+    EXPECT_CALL(*client_b_, OnStarted(_));
+    device_client_->OnStarted();
+
+    // VideoCaptureController will take care of the OnStarted event for the
+    // clients who join later.
+    EXPECT_CALL(*client_a_, OnStarted(_));
+    controller_->AddClient(client_a_route_2, client_a_.get(), 200, session_200);
+  }
+}
 }  // namespace content