Fix screen capture slowness in Chrome OS feedback report.

content/browser/renderer_host/media/video_capture_device_impl.cc

Index: content/browser/renderer_host/media/video_capture_device_impl.cc
diff --git a/content/browser/renderer_host/media/video_capture_device_impl.cc b/content/browser/renderer_host/media/video_capture_device_impl.cc
index 54af30f71b461e6ad74bfa760c18c8dcc832cb45..7896fb19f2681c50d6ed1bdedca1b07a12dc4090 100644
--- a/content/browser/renderer_host/media/video_capture_device_impl.cc
+++ b/content/browser/renderer_host/media/video_capture_device_impl.cc
@@ -44,12 +44,15 @@ void DeleteCaptureMachineOnUIThread(
 ThreadSafeCaptureOracle::ThreadSafeCaptureOracle(
     scoped_ptr<media::VideoCaptureDevice::Client> client,
     scoped_ptr<VideoCaptureOracle> oracle,
-    const gfx::Size& capture_size,
+    const gfx::Size& max_frame_size,
     int frame_rate)
     : client_(client.Pass()),
       oracle_(oracle.Pass()),
-      capture_size_(capture_size),
-      frame_rate_(frame_rate) {}
+      max_frame_size_(max_frame_size),
+      frame_rate_(frame_rate) {
+  // Set initial capture size to maximum frame size.
+  capture_size_ = max_frame_size_;
+}
 
 ThreadSafeCaptureOracle::~ThreadSafeCaptureOracle() {}
 
@@ -122,6 +125,16 @@ bool ThreadSafeCaptureOracle::ObserveEventAndDecideCapture(
   return true;
 }
 
+void ThreadSafeCaptureOracle::UpdateCaptureSize(const gfx::Size& source_size) {
+  base::AutoLock guard(lock_);
+
+  // The capture resolution should not exceed the source frame size.
+  // In other words it should downscale the image but not upscale it.
+  gfx::Size capture_size = max_frame_size_;
+  capture_size.SetToMin(source_size);
+  capture_size_ = capture_size;
+}
+
 void ThreadSafeCaptureOracle::Stop() {
   base::AutoLock guard(lock_);
   client_.reset();