Take advantage of XDAMAGE to support Screen Capture under ChromeOS.

media/video/capture/screen/screen_capture_device.cc

Index: media/video/capture/screen/screen_capture_device.cc
diff --git a/media/video/capture/screen/screen_capture_device.cc b/media/video/capture/screen/screen_capture_device.cc
index 6182f8d4e0e4f710d85831ed56cbddffa630f964..c831d03cd066eac8878e9562d53d57eccc635dc7 100644
--- a/media/video/capture/screen/screen_capture_device.cc
+++ b/media/video/capture/screen/screen_capture_device.cc
@@ -271,8 +271,15 @@ void ScreenCaptureDevice::Core::DoAllocate(int frame_rate) {
   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);