Enable RTCVideoDecoder SW H264 fallback only when it is available

content/renderer/media/webrtc/peer_connection_dependency_factory.cc

 // Copyright 2014 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/webrtc/peer_connection_dependency_factory.h"
 
 #include <stddef.h>
 
 #include <utility>
 #include <vector>
@@ skipping 146 matching lines @@
   DCHECK(!worker_thread_);
   DCHECK(!network_manager_);
   DCHECK(!socket_factory_);
   DCHECK(!chrome_signaling_thread_.IsRunning());
   DCHECK(!chrome_worker_thread_.IsRunning());
 
   DVLOG(1) << "PeerConnectionDependencyFactory::CreatePeerConnectionFactory()";
 
 #if BUILDFLAG(RTC_USE_H264)
   // Building /w |rtc_use_h264|, is the corresponding run-time feature enabled?
-  if (base::FeatureList::IsEnabled(kWebRtcH264WithOpenH264FFmpeg)) {
+  if (base::FeatureList::IsEnabled(kWebRtcH264WithOpenH264FFmpeg) ||
+      base::CommandLine::ForCurrentProcess()->HasSwitch(
+          kEnableWebRtcHWH264Encoding)) {

[hbos_chromium, 2016/06/02 08:45:37]

I don't think this is the right approach. If we're building with SW H264, one
feature unexpectedly enables another feature (that might be set to disabled
which is strange). If we're not building with SW H264 (such as chromium build
instead of a chrome official) this does not fix anything, we still have the
problem of trying to do SW fallback when SW is not available.

I'll continue the discussion at
https://bugs.chromium.org/p/chromium/issues/detail?id=615513

[emircan, 2016/06/02 20:54:32]

Done.

     // |H264DecoderImpl| may be used which depends on FFmpeg, therefore we need
     // to initialize FFmpeg before going further.
     media::FFmpegGlue::InitializeFFmpeg();
   } else {
     // Feature is to be disabled, no need to make sure FFmpeg is initialized.
     webrtc::DisableRtcUseH264();
   }
 #endif
 
   base::MessageLoop::current()->AddDestructionObserver(this);
@@ skipping 391 matching lines @@
 
 void PeerConnectionDependencyFactory::EnsureWebRtcAudioDeviceImpl() {
   DCHECK(CalledOnValidThread());
   if (audio_device_.get())
     return;
 
   audio_device_ = new WebRtcAudioDeviceImpl();
 }
 
 }  // namespace content