Enable QP parsing from CABAC bitstreams

webrtc/common_video/h264/h264_bitstream_parser.cc

Index: webrtc/common_video/h264/h264_bitstream_parser.cc
diff --git a/webrtc/common_video/h264/h264_bitstream_parser.cc b/webrtc/common_video/h264/h264_bitstream_parser.cc
index 5f89c50af14835c73b6bd20bbb312f7dd7a3b6b5..048cdd2f6ea58da64b7d4b37507c2e6078a88865 100644
--- a/webrtc/common_video/h264/h264_bitstream_parser.cc
+++ b/webrtc/common_video/h264/h264_bitstream_parser.cc
@@ -242,9 +242,12 @@ H264BitstreamParser::Result H264BitstreamParser::ParseNonParameterSetNalu(
       }
     }
   }
-  // cabac not supported: entropy_coding_mode_flag == 0 asserted above.
-  // if (entropy_coding_mode_flag && slice_type != I && slice_type != SI)
-  //   cabac_init_idc
+  if (pps_->entropy_coding_mode_flag &&
+      slice_type != H264::SliceType::kI && slice_type != H264::SliceType::kSi) {
+    // cabac_init_idc: ue(v)
+    RETURN_INV_ON_FAIL(slice_reader.ReadExponentialGolomb(&golomb_tmp));
+  }
+
   int32_t last_slice_qp_delta;
   RETURN_INV_ON_FAIL(
       slice_reader.ReadSignedExponentialGolomb(&last_slice_qp_delta));