Canvas captureStream() to capture a frame in the start

third_party/WebKit/Source/modules/mediacapturefromelement/HTMLCanvasElementCapture.cpp

 // 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 "modules/mediacapturefromelement/HTMLCanvasElementCapture.h"
 
 #include "core/dom/ExceptionCode.h"
 #include "core/html/HTMLCanvasElement.h"
 #include "modules/mediacapturefromelement/CanvasCaptureMediaStreamTrack.h"
 #include "modules/mediastream/MediaStream.h"
@@ skipping 41 matching lines @@
     if (!handler) {
         exceptionState.throwDOMException(NotSupportedError, "No CanvasCapture handler can be created.");
         return nullptr;
     }
 
     MediaStreamTrackVector tracks;
     if (givenFrameRate)
         tracks.append(CanvasCaptureMediaStreamTrack::create(track, &element, handler.release(), frameRate));
     else
         tracks.append(CanvasCaptureMediaStreamTrack::create(track, &element, handler.release()));
+    // We want to capture one frame in the beginning.
+    element.notifyListenersCanvasChanged();
     return MediaStream::create(element.executionContext(), tracks);
 }
 
 } // namespace blink