Add fix for 8-bit H264 HDR content

8-bit H264 HDR content is not rendered correctly in Chrome on Windows.
This is a temporary fix that converts the 8-bit buffer to a 10-bit
buffer if the color space indicates that the buffer should be
rendered as HDR.

Bug: webrtc:10575
Change-Id: I106612ec489c6371fa774424a4cf07d9bad40fc3
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/134040
Commit-Queue: Johannes Kron <kron@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27766}

modules/video_coding/codecs/h264/h264_decoder_impl.h

@@ -68,6 +68,7 @@ class H264DecoderImpl : public H264Decoder {
   const char* ImplementationName() const override;
 
  private:
+  const bool kEnable8bitHdrFix_;
   // Called by FFmpeg when it needs a frame buffer to store decoded frames in.
   // The |VideoFrame| returned by FFmpeg at |Decode| originate from here. Their
   // buffers are reference counted and freed by FFmpeg using |AVFreeBuffer2|.