Fix crop bug in WebRtcVideoCapturerAdapter

In the current code, CPU adaptation does not work correctly. It should
scale to the adapted resolution, but it crops instead. The result looks
like zoomed in video. This bug was introduced in
https://codereview.chromium.org/2270723002/.

This CL fixes the cropping logic.

BUG=chromium:635592

Review-Url: https://codereview.chromium.org/2323573004
Cr-Commit-Position: refs/heads/master@{#417549}

content/renderer/media/webrtc/webrtc_video_capturer_adapter.cc

@@ -136,8 +136,7 @@ void WebRtcVideoCapturerAdapter::OnFrameCaptured(
   // Return |frame| directly if it is GpuMemoryBuffer backed, as we want to
   // keep the frame on native buffers.
   if (frame->HasTextures() ||
-      frame->storage_type() ==
-      media::VideoFrame::STORAGE_GPU_MEMORY_BUFFERS) {
+      frame->storage_type() == media::VideoFrame::STORAGE_GPU_MEMORY_BUFFERS) {
     OnFrame(cricket::WebRtcVideoFrame(
                 new rtc::RefCountedObject<WebRtcVideoFrameAdapter>(frame),
                 webrtc::kVideoRotation_0, translated_camera_time_us),
@@ -145,17 +144,19 @@ void WebRtcVideoCapturerAdapter::OnFrameCaptured(
     return;
   }
 
-  // Create a centered cropped visible rect that preservers aspect ratio for
-  // cropped natural size.
-  gfx::Rect visible_rect = frame->visible_rect();
-  visible_rect.ClampToCenteredSize(gfx::Size(
-      visible_rect.width() * adapted_width / orig_width,
-      visible_rect.height() * adapted_height / orig_height));
+  // Translate crop rectangle from natural size to visible size.
+  gfx::Rect cropped_visible_rect(
+      frame->visible_rect().x() +
+          crop_x * frame->visible_rect().width() / orig_width,
+      frame->visible_rect().y() +
+          crop_y * frame->visible_rect().height() / orig_height,
+      crop_width * frame->visible_rect().width() / orig_width,
+      crop_height * frame->visible_rect().height() / orig_height);
 
   const gfx::Size adapted_size(adapted_width, adapted_height);
   scoped_refptr<media::VideoFrame> video_frame =
       media::VideoFrame::WrapVideoFrame(frame, frame->format(),
-                                        visible_rect, adapted_size);
+                                        cropped_visible_rect, adapted_size);
   if (!video_frame)
     return;