Tab/Desktop Capture: Use requests instead of timer-based refreshing.

media/capture/content/screen_capture_device_core.cc

Index: media/capture/content/screen_capture_device_core.cc
diff --git a/media/capture/content/screen_capture_device_core.cc b/media/capture/content/screen_capture_device_core.cc
index 2b3f3cfaecfe3e799e2ef4821a7a1f93b23e5f09..6e9f3355888d0f0a36cd1e3ce5202aae7d1f6490 100644
--- a/media/capture/content/screen_capture_device_core.cc
+++ b/media/capture/content/screen_capture_device_core.cc
@@ -65,6 +65,17 @@ void ScreenCaptureDeviceCore::AllocateAndStart(
   TransitionStateTo(kCapturing);
 }
 
+void ScreenCaptureDeviceCore::RequestRefreshFrame() {

[Irfan, 2016/04/06 19:53:05]

Any value in providing feedback when the request is dropped ?

[miu, 2016/04/06 22:33:53]

No.  The request originates in the renderer process and is meant to be a
one-way-communication and best-effort scheme.  There's documentation in the IPCs
and VideoCaptureDevice interface to explain further.

+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  if (state_ != kCapturing)
+    return;
+
+  if (oracle_proxy_->AttemptPassiveRefresh())
+    return;
+  capture_machine_->MaybeCaptureForRefresh();
+}
+
 void ScreenCaptureDeviceCore::StopAndDeAllocate() {
   DCHECK(thread_checker_.CalledOnValidThread());