Rotate frames correctly for back camera

media/capture/video/video_capture_device_client.cc

Index: media/capture/video/video_capture_device_client.cc
diff --git a/media/capture/video/video_capture_device_client.cc b/media/capture/video/video_capture_device_client.cc
index 215785ea4f72f144c3cb16c4220e1e170271e0d4..3ef8fc5d2732d188133419b69703160596f39b4a 100644
--- a/media/capture/video/video_capture_device_client.cc
+++ b/media/capture/video/video_capture_device_client.cc
@@ -80,6 +80,7 @@ VideoCaptureDeviceClient::VideoCaptureDeviceClient(
       jpeg_decoder_factory_callback_(jpeg_decoder_factory),
       external_jpeg_decoder_initialized_(false),
       buffer_pool_(buffer_pool),
+      is_back_camera_(false),
       last_captured_pixel_format_(media::PIXEL_FORMAT_UNKNOWN) {}
 
 VideoCaptureDeviceClient::~VideoCaptureDeviceClient() {
@@ -133,6 +134,14 @@ void VideoCaptureDeviceClient::OnIncomingCapturedData(
 
   DCHECK_EQ(0, rotation % 90) << " Rotation must be a multiple of 90, now: "
                               << rotation;
+
+  if (is_back_camera_) {
+    // For back camera, we need to rotate (360 - screen_rotation).
+    // Ex: when screen rotation is 90, we have to rotate the frame by 270
+    // clockwise.
+    rotation = (360 - rotation) % 360;

[wuchengli, 2016/11/16 12:15:19]

Can we calculate the right rotation in VideoCaptureDeviceLinux and pass it to
VideoCaptureDeviceClient::OnIncomingCapturedData?

[shenghao, 2016/11/17 08:41:45]

Done.

+  }
+
   libyuv::RotationMode rotation_mode = libyuv::kRotate0;
   if (rotation == 90)
     rotation_mode = libyuv::kRotate90;
@@ -355,6 +364,10 @@ double VideoCaptureDeviceClient::GetBufferPoolUtilization() const {
   return buffer_pool_->GetBufferPoolUtilization();
 }
 
+void VideoCaptureDeviceClient::SetCameraFacing(bool is_back_camera) {
+  is_back_camera_ = is_back_camera;
+}
+
 std::unique_ptr<media::VideoCaptureDevice::Client::Buffer>
 VideoCaptureDeviceClient::ReserveI420OutputBuffer(
     const gfx::Size& dimensions,