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

media/capture/content/screen_capture_device_core.cc

 // Copyright 2014 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 "media/capture/content/screen_capture_device_core.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/logging.h"
@@ skipping 47 matching lines @@
   oracle_proxy_ = new ThreadSafeCaptureOracle(
       std::move(client), params, capture_machine_->IsAutoThrottlingEnabled());
 
   capture_machine_->Start(
       oracle_proxy_, params,
       base::Bind(&ScreenCaptureDeviceCore::CaptureStarted, AsWeakPtr()));
 
   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());
 
   if (state_ != kCapturing)
     return;
 
   oracle_proxy_->Stop();
   oracle_proxy_ = NULL;
 
   TransitionStateTo(kIdle);
@@ skipping 45 matching lines @@
     return;
 
   if (oracle_proxy_.get())
     oracle_proxy_->ReportError(from_here, reason);
 
   StopAndDeAllocate();
   TransitionStateTo(kError);
 }
 
 }  // namespace media