Implement transferToImageBitmap() in WebGLRenderingContext

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp

Index: third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
index 4f64e965baee7d050d1238d96baa164b5d28447a..4e205b775b80ae510b6d8333d1ea5244d249c49c 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
@@ -634,6 +634,16 @@ void WebGLRenderingContextBase::forceNextWebGLContextCreationToFail()
     shouldFailContextCreationForTesting = true;
 }
 
+ImageBitmap* WebGLRenderingContextBase::transferToImageBitmapBase()
+{
+    if (!drawingBuffer())
+        return nullptr;
+    WebExternalTextureMailbox mailbox;
+    drawingBuffer()->prepareMailbox(&mailbox, 0);
+    ImageBitmap* imageBitmap = ImageBitmap::create(mailbox);
+    return imageBitmap;

[Ken Russell (switch to Gerrit), 2016/05/19 00:15:11]

This is a good start. Please add a TODO like:

TODO(xidachen): create a small pool of recycled textures from
ImageBitmapRenderingContext's transferFromImageBitmap, and try to use them in
DrawingBuffer. This will avoid texture re-allocation in the steady state when
repeatedly transferring frames from a WebGLRenderingContext to an
ImageBitmapRenderingContext.

[xidachen, 2016/05/19 13:48:29]

Done.

+}
+
 namespace {
 
 // ES2 enums
@@ -1165,6 +1175,9 @@ void WebGLRenderingContextBase::markContextChanged(ContentChangeType changeType)
 
     drawingBuffer()->markContentsChanged();
 
+    if (!canvas())
+        return;
+
     LayoutBox* layoutBox = canvas()->layoutBox();
     if (layoutBox && layoutBox->hasAcceleratedCompositing()) {
         m_markedCanvasDirty = true;