Pass camera facing to WebKit

content/renderer/media/media_stream_video_track.cc

 // Copyright 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 "content/renderer/media/media_stream_video_track.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/location.h"
@@ skipping 289 matching lines @@
 }
 
 void MediaStreamVideoTrack::getSettings(
     blink::WebMediaStreamTrack::Settings& settings) {
   if (source_) {
     const media::VideoCaptureFormat* format = source_->GetCurrentFormat();
     if (format) {
       settings.frameRate = format->frame_rate;
       settings.width = format->frame_size.width();
       settings.height = format->frame_size.height();
+      const media::VideoFacingMode facing = source_->GetVideoFacing();
+      switch (facing) {
+        case media::VideoFacingMode::USER:
+          settings.facingMode =
+              blink::WebMediaStreamTrack::Settings::VideoFacingMode::User;
+          break;
+        case media::VideoFacingMode::ENVIRONMENT:
+          settings.facingMode = blink::WebMediaStreamTrack::Settings::
+              VideoFacingMode::Environment;
+          break;
+        case media::VideoFacingMode::LEFT:
+          settings.facingMode =
+              blink::WebMediaStreamTrack::Settings::VideoFacingMode::Left;
+          break;
+        case media::VideoFacingMode::RIGHT:
+          settings.facingMode =
+              blink::WebMediaStreamTrack::Settings::VideoFacingMode::Right;
+          break;
+      }

[mcasas, 2017/01/11 22:24:58]

And here, if we get a media::VideoFacingMode::None, don't
fill in |facing|. Which should do the trick assuming it has been 
changed to base::Optional<> as mentioned elsewhere.

[shenghao, 2017/01/12 08:10:48]

Done.

     }
   }
   // TODO(hta): Extract the real value.
   settings.deviceId = blink::WebString("video device ID");
 }
 
 void MediaStreamVideoTrack::OnReadyStateChanged(
     blink::WebMediaStreamSource::ReadyState state) {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   for (auto* sink : sinks_)
     sink->OnReadyStateChanged(state);
 }
 
 }  // namespace content