Handle early destruction of CanvasCaptureHandler

content/renderer/media/canvas_capture_handler.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/renderer/media/canvas_capture_handler.h"
 
 #include <utility>
 
 #include "base/base64.h"
 #include "base/bind_helpers.h"
 #include "base/macros.h"
 #include "base/rand_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "content/public/renderer/render_thread.h"
 #include "content/renderer/media/media_stream_video_capturer_source.h"
 #include "content/renderer/media/media_stream_video_source.h"
 #include "content/renderer/media/media_stream_video_track.h"
 #include "content/renderer/media/webrtc_uma_histograms.h"
 #include "content/renderer/render_thread_impl.h"
 #include "third_party/WebKit/public/platform/WebMediaStreamSource.h"
 #include "third_party/WebKit/public/platform/WebString.h"
 #include "third_party/libyuv/include/libyuv.h"
 
 namespace content {
 
 class CanvasCaptureHandler::VideoCapturerSource

[mcasas, 2016/03/23 17:54:30]

nit: could you add a comment saying that
this class is single threaded? If you take
my suggestion in the .h file, also this class
won't need to be CanvasCaptureHandler::

[emircan, 2016/03/23 22:12:03]

Done.

     : public media::VideoCapturerSource {
  public:
   explicit VideoCapturerSource(base::WeakPtr<CanvasCaptureHandler>
                                    canvas_handler,
                                double frame_rate)
       : frame_rate_(frame_rate),
         canvas_handler_(canvas_handler) {}
 
  protected:
   void GetCurrentSupportedFormats(
@@ skipping 14 matching lines @@
   }
   void StartCapture(const media::VideoCaptureParams& params,
                     const VideoCaptureDeliverFrameCB& frame_callback,
                     const RunningCallback& running_callback) override {
     DCHECK(main_render_thread_checker_.CalledOnValidThread());
     canvas_handler_->StartVideoCapture(params, frame_callback,
                                        running_callback);
   }
   void StopCapture() override {
     DCHECK(main_render_thread_checker_.CalledOnValidThread());
-    canvas_handler_->StopVideoCapture();
+    if (canvas_handler_.get())
+      canvas_handler_->StopVideoCapture();
   }
 
  private:
   double frame_rate_;

[mcasas, 2016/03/23 17:54:30]

const? :)

[emircan, 2016/03/23 22:12:03]

Done :)

   // Bound to Main Render thread.
   base::ThreadChecker main_render_thread_checker_;
-  // CanvasCaptureHandler is owned by CanvasDrawListener in blink and
-  // guaranteed to be alive during the lifetime of this class.
+  // CanvasCaptureHandler is owned by CanvasDrawListener in blink and might be
+  // destructed before StopCapture() call.

[mcasas, 2016/03/23 17:54:30]

nit: s/destructed/destroyed/ ?

[emircan, 2016/03/23 22:12:03]

Done.

   base::WeakPtr<CanvasCaptureHandler> canvas_handler_;
 };
 
 class CanvasCaptureHandler::CanvasCaptureHandlerDelegate {
  public:
   explicit CanvasCaptureHandlerDelegate(
       media::VideoCapturerSource::VideoCaptureDeliverFrameCB new_frame_callback)
       : new_frame_callback_(new_frame_callback),
         weak_ptr_factory_(this) {
     io_thread_checker_.DetachFromThread();
@@ skipping 158 matching lines @@
 
   web_track->initialize(webkit_source);
   blink::WebMediaConstraints constraints;
   constraints.initialize();
   web_track->setExtraData(new MediaStreamVideoTrack(
       media_stream_source.release(), constraints,
       MediaStreamVideoSource::ConstraintsCallback(), true));
 }
 
 }  // namespace content