Add flag to enable MJPEG acceleration for video capture

content/browser/renderer_host/media/video_capture_gpu_jpeg_decoder.cc

 // Copyright 2015 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/browser/renderer_host/media/video_capture_gpu_jpeg_decoder.h"
 
 #include "base/bind.h"
+#include "base/command_line.h"
 #include "base/logging.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/stringprintf.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
 #include "content/browser/gpu/browser_gpu_channel_host_factory.h"
 #include "content/common/gpu/client/gpu_jpeg_decode_accelerator_host.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/common/content_switches.h"
 #include "media/base/video_frame.h"
 
 namespace content {
 
 // static
 bool VideoCaptureGpuJpegDecoder::Supported() {
   // A lightweight check for caller to avoid IPC latency for known unsupported
   // platform. Initialize() can do the real platform supporting check but it
   // requires an IPC even for platforms that do not support HW decoder.
   // TODO(kcwu): move this information to GpuInfo. https://crbug.com/503568
+#if defined(OS_CHROMEOS) && defined(ARCH_CPU_X86_FAMILY)
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableAcceleratedMjpegDecode)) {
+    return true;
+  }
+#endif
   return false;
 }
 
 VideoCaptureGpuJpegDecoder::VideoCaptureGpuJpegDecoder(
     const DecodeDoneCB& decode_done_cb,
     const ErrorCB& error_cb)
     : decode_done_cb_(decode_done_cb),
       error_cb_(error_cb),
       next_bitstream_buffer_id_(0),
       in_buffer_id_(media::JpegDecodeAccelerator::kInvalidBitstreamBufferId) {
@@ skipping 180 matching lines @@
     decode_done_closure_ = base::Bind(
         decode_done_cb_, base::Passed(&out_buffer), out_frame, timestamp);
   }
   decoder_->Decode(in_buffer, out_frame);
 #else
   NOTREACHED();
 #endif
 }
 
 }  // namespace content