Implement a source for remote video tracks.

content/renderer/media/media_stream_video_source.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/media_stream_video_source.h"
 
 #include <algorithm>
 #include <limits>
 #include <string>
 
@@ skipping 270 matching lines @@
 MediaStreamVideoSource* MediaStreamVideoSource::GetVideoSource(
     const blink::WebMediaStreamSource& source) {
   return static_cast<MediaStreamVideoSource*>(source.extraData());
 }
 
 MediaStreamVideoSource::MediaStreamVideoSource(
     MediaStreamDependencyFactory* factory)
     : state_(NEW),
       factory_(factory),
       capture_adapter_(NULL) {
-  DCHECK(factory_);
 }
 
 MediaStreamVideoSource::~MediaStreamVideoSource() {
 }
 
 void MediaStreamVideoSource::AddTrack(
     MediaStreamVideoTrack* track,
     const blink::WebMediaConstraints& constraints,
     const ConstraintsCallback& callback) {
   DCHECK(CalledOnValidThread());
@@ skipping 44 matching lines @@
 void MediaStreamVideoSource::InitAdapter() {
   if (adapter_)
     return;
   // Create the webrtc::MediaStreamVideoSourceInterface adapter.
   // It needs the constraints so that constraints used by a PeerConnection
   // will be available such as constraints for CPU adaptation and a tab
   // capture.
   bool is_screeencast =
       device_info().device.type == MEDIA_TAB_VIDEO_CAPTURE ||
       device_info().device.type == MEDIA_DESKTOP_VIDEO_CAPTURE;
   capture_adapter_ = factory_->CreateVideoCapturer(is_screeencast);

[Ronghua Wu (Left Chromium), 2014/03/17 22:45:35]

since we no longer assert factory_, we should check factory_ before use

[perkj_chrome, 2014/03/19 16:34:48]

Other reviewers typically say that is no need. Since it will be obvious in the
crash that it is a null pointer.

[Ronghua Wu (Left Chromium), 2014/03/20 21:55:50]

ok. :)

   capture_adapter_->SetRequestedFormat(current_format_);
   adapter_ = factory_->CreateVideoSource(capture_adapter_,
                                          current_constraints_);
 }
 
 webrtc::VideoSourceInterface* MediaStreamVideoSource::GetAdapter() {
   if (!adapter_) {
     InitAdapter();
   }
   return adapter_;
@@ skipping 150 matching lines @@
 MediaStreamVideoSource::RequestedConstraints::RequestedConstraints(
     const blink::WebMediaConstraints& constraints,
     const ConstraintsCallback& callback)
     : constraints(constraints), callback(callback) {
 }
 
 MediaStreamVideoSource::RequestedConstraints::~RequestedConstraints() {
 }
 
 }  // namespace content