Add video frame refresh to MediaStream and VideoCapture stacks.

content/browser/renderer_host/media/video_capture_manager.cc

Index: content/browser/renderer_host/media/video_capture_manager.cc
diff --git a/content/browser/renderer_host/media/video_capture_manager.cc b/content/browser/renderer_host/media/video_capture_manager.cc
index 4016235c8f8bc5d0fe09c6d4ddb9674612449837..6f728b28101d993266656270a50da7186744a93e 100644
--- a/content/browser/renderer_host/media/video_capture_manager.cc
+++ b/content/browser/renderer_host/media/video_capture_manager.cc
@@ -668,6 +668,24 @@ void VideoCaptureManager::ResumeCaptureForClient(
   controller->ResumeClient(client_id, client_handler);
 }
 
+void VideoCaptureManager::RequestRefreshFrameForClient(
+    VideoCaptureController* controller) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+
+  if (DeviceEntry* entry = GetDeviceEntryForController(controller)) {
+    if (media::VideoCaptureDevice* device = entry->video_capture_device()) {
+      device_task_runner_->PostTask(
+          FROM_HERE,
+          base::Bind(&media::VideoCaptureDevice::RequestRefreshFrame,

[xjz, 2016/04/05 00:04:43]

VideoCaptureDevice::RequestRefreshFrame() currently is a virtual function with
default no-op implementation (and no other implementations anywhere else). Are
the changes on it going to be in follow up CLs?

[miu, 2016/04/05 20:25:01]

Yep!  :)  I'll ask you to review that one shortly.

+                     // Unretained is safe to use here because |device| would be
+                     // null if it was scheduled for shutdown and destruction,
+                     // and because this task is guaranteed to run before the
+                     // task that destroys the |device|.
+                     base::Unretained(device)));
+    }
+  }
+}
+
 bool VideoCaptureManager::GetDeviceSupportedFormats(
     media::VideoCaptureSessionId capture_session_id,
     media::VideoCaptureFormats* supported_formats) {