Take advantage of XDAMAGE to support Screen Capture under ChromeOS.

media/video/capture/screen/screen_capture_device.cc

 // Copyright (c) 2013 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/video/capture/screen/screen_capture_device.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/sequenced_task_runner.h"
@@ skipping 253 matching lines @@
   // frame. crbug.com/173265 .
   DCHECK(task_runner_->RunsTasksOnCurrentThread());
 }
 
 void ScreenCaptureDevice::Core::DoAllocate(int frame_rate) {
   DCHECK(task_runner_->RunsTasksOnCurrentThread());
 
   frame_rate_ = frame_rate;
 
   // Create and start frame capturer.
+#if defined(OS_CHROMEOS)
+  // ScreenCapturerX11 polls by default, due to poor driver support for DAMAGE.
+  // ChromeOS' drivers [can be patched to] support DAMAGE properly, so use it.
+  if (!screen_capturer_)

[Sergey Ulanov, 2013/03/17 05:36:32]

nit: Maybe pull this line out of the #ifdef - it's common between the two cases.

[Wez, 2013/03/19 18:25:44]

Since it's only duplicating one line, I chose to avoid splitting the if from the
code it executes.

+    screen_capturer_ = ScreenCapturer::CreateWithXDamage(true);
+#else
   if (!screen_capturer_)
     screen_capturer_ = ScreenCapturer::Create();
+#endif
   if (screen_capturer_)
     screen_capturer_->Start(this);
 
   // Capture first frame, so that we can call OnFrameInfo() callback.
   waiting_for_frame_size_ = true;
   DoCapture();
 }
 
 void ScreenCaptureDevice::Core::DoStart() {
   DCHECK(task_runner_->RunsTasksOnCurrentThread());
@@ skipping 85 matching lines @@
 
 void ScreenCaptureDevice::DeAllocate() {
   core_->DeAllocate();
 }
 
 const VideoCaptureDevice::Name& ScreenCaptureDevice::device_name() {
   return name_;
 }
 
 }  // namespace media