Add TimedCanvasDrawListener

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

Index: third_party/WebKit/Source/modules/mediacapturefromelement/HTMLCanvasElementCapture.cpp
diff --git a/third_party/WebKit/Source/modules/mediacapturefromelement/HTMLCanvasElementCapture.cpp b/third_party/WebKit/Source/modules/mediacapturefromelement/HTMLCanvasElementCapture.cpp
index d199fdfe2c4ac30f4bae66c9cfe3183b7e842770..1c3a896c879f47679534d7fc2d605a7fabaa837b 100644
--- a/third_party/WebKit/Source/modules/mediacapturefromelement/HTMLCanvasElementCapture.cpp
+++ b/third_party/WebKit/Source/modules/mediacapturefromelement/HTMLCanvasElementCapture.cpp
@@ -22,6 +22,16 @@ namespace blink {
 
 MediaStream* HTMLCanvasElementCapture::captureStream(HTMLCanvasElement& element, ExceptionState& exceptionState)
 {
+    return HTMLCanvasElementCapture::captureStream(element, false, kDefaultFrameRate, exceptionState);

[esprehn, 2015/12/15 23:58:01]

Hmmm that bool seems like it should be an enum, it's not clear from here what
the true vs false does.

Actually lets just add two separate methods, one that takes a frameRate and one
that doesn't.

[emircan, 2015/12/16 15:36:21]

I am adding "if (givenFrameRate)" cases to avoid code duplication. I explained
the use of kDefaultFrameRate below.

+}
+
+MediaStream* HTMLCanvasElementCapture::captureStream(HTMLCanvasElement& element, double frameRate, ExceptionState& exceptionState)
+{
+    return HTMLCanvasElementCapture::captureStream(element, true, frameRate, exceptionState);
+}
+
+MediaStream* HTMLCanvasElementCapture::captureStream(HTMLCanvasElement& element, bool givenFrameRate, double frameRate, ExceptionState& exceptionState)
+{
     if (!element.originClean()) {
         exceptionState.throwDOMException(SecurityError, "Canvas is not origin-clean.");
         return MediaStream::create(element.executionContext());
@@ -29,7 +39,7 @@ MediaStream* HTMLCanvasElementCapture::captureStream(HTMLCanvasElement& element,
 
     WebMediaStreamTrack track;
     WebSize size(element.width(), element.height());
-    OwnPtr<WebCanvasCaptureHandler> handler = adoptPtr(Platform::current()->createCanvasCaptureHandler(size, kDefaultFrameRate, &track));
+    OwnPtr<WebCanvasCaptureHandler> handler = adoptPtr(Platform::current()->createCanvasCaptureHandler(size, frameRate, &track));

[esprehn, 2015/12/15 23:58:01]

you pass frameRate here even if givenFrameRate is false, how does it know? It
seems like you can just use a magic number for frameRate instead if its okay to
do it here.

[emircan, 2015/12/16 15:36:21]

This is some confusing part, more related to VideoCapturerSource than this spec.
captureStream() case doesn't have a frame rate, but VideoCapturerSource
implementation requires to return a frame rate [0]. <canvas> doesn't have a
frame rate and when it is not specified here, I return a default value.

[0]
https://code.google.com/p/chromium/codesearch#chromium/src/content/renderer/m...

     ASSERT(handler);
     if (!handler) {
         exceptionState.throwDOMException(NotSupportedError, "No CanvasCapture handler can be created.");
@@ -37,7 +47,7 @@ MediaStream* HTMLCanvasElementCapture::captureStream(HTMLCanvasElement& element,
     }
 
     MediaStreamTrackVector tracks;
-    tracks.append(CanvasCaptureMediaStreamTrack::create(track, &element, handler.release()));
+    tracks.append(CanvasCaptureMediaStreamTrack::create(track, &element, handler.release(), givenFrameRate, frameRate));

[esprehn, 2015/12/15 23:58:01]

Split this method into two methods, one for frameRate and one without.

[emircan, 2015/12/16 15:36:21]

Done.

     return MediaStream::create(element.executionContext(), tracks);
 }