Basic use implementation for MediaStream from Canvas: captureStream()

third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
index 3b5b5c4d0c1f043cee3d8dff903fc75d1bff9dfe..a4cf6dee2a14d274e7be11a4520aab3b9871ca3a 100644
--- a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
@@ -283,6 +283,8 @@ void HTMLCanvasElement::didDraw(const FloatRect& rect)
 
 void HTMLCanvasElement::didFinalizeFrame()
 {
+    notifyListenersCanvasChanged();
+
     if (m_dirtyRect.isEmpty())
         return;
 
@@ -393,13 +395,41 @@ bool HTMLCanvasElement::paintsIntoCanvasBuffer() const
 
     if (!m_context->isAccelerated())
         return true;
-
     if (layoutBox() && layoutBox()->hasAcceleratedCompositing())
         return false;
 
     return true;
 }
 
+void HTMLCanvasElement::notifyListenersCanvasChanged()
+{
+    if (!originClean()) {
+        m_listeners.clear();
+        return;
+    }
+
+    bool listenerNeedsNewFrameCapture = false;
+    for (const CanvasDrawListener* listener : m_listeners) {
+        if (listener->needsNewFrame()) {
+            listenerNeedsNewFrameCapture = true;
+        }
+    }
+
+    if (listenerNeedsNewFrameCapture) {
+        SourceImageStatus status;
+        RefPtr<Image> sourceImage = getSourceImageForCanvas(&status, PreferNoAcceleration);
+        if (status != NormalSourceImageStatus)
+            return;
+        RefPtr<SkImage> image = sourceImage->imageForCurrentFrame();
+        for (CanvasDrawListener* listener : m_listeners) {
+            if (listener->needsNewFrame()) {
+                listener->sendNewFrame(image);
+            }
+        }
+    }
+
+}
+
 void HTMLCanvasElement::paint(GraphicsContext* context, const LayoutRect& r)
 {
     // FIXME: crbug.com/438240; there is a bug with the new CSS blending and compositing feature.
@@ -566,6 +596,16 @@ void HTMLCanvasElement::toBlob(FileCallback* callback, const String& mimeType, c
     asyncCreatorRef->scheduleAsyncBlobCreation(false, quality);
 }
 
+void HTMLCanvasElement::addListener(CanvasDrawListener* listener)
+{
+    m_listeners.add(listener);
+}
+
+void HTMLCanvasElement::removeListener(CanvasDrawListener* listener)
+{
+    m_listeners.remove(listener);
+}
+
 SecurityOrigin* HTMLCanvasElement::securityOrigin() const
 {
     return document().securityOrigin();
@@ -741,6 +781,7 @@ void HTMLCanvasElement::notifySurfaceInvalid()
 
 DEFINE_TRACE(HTMLCanvasElement)
 {
+    visitor->trace(m_listeners);
     visitor->trace(m_context);
     DocumentVisibilityObserver::trace(visitor);
     HTMLElement::trace(visitor);