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..1d919f2e387d265dd450c150e528b2d3bd3634b5 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
@@ -634,6 +634,18 @@ void WebGLRenderingContextBase::forceNextWebGLContextCreationToFail()
     shouldFailContextCreationForTesting = true;
 }
 
+ImageBitmap* WebGLRenderingContextBase::transferToImageBitmapBase()
+{
+    if (!drawingBuffer())
+        return nullptr;
+    WebExternalTextureMailbox mailbox;
+    drawingBuffer()->prepareMailbox(&mailbox, 0);
+    ImageBitmap* imageBitmap = ImageBitmap::create(mailbox);
+    // TODO(xidachen): Create a small pool of recycled textures from ImageBitmapRenderingContext's
+    // transferFromImageBitmap, and try to use them in DrawingBuffer.
+    return imageBitmap;
+}
+
 namespace {
 
 // ES2 enums
@@ -1165,6 +1177,9 @@ void WebGLRenderingContextBase::markContextChanged(ContentChangeType changeType)
 
     drawingBuffer()->markContentsChanged();
 
+    if (!canvas())
+        return;
+
     LayoutBox* layoutBox = canvas()->layoutBox();
     if (layoutBox && layoutBox->hasAcceleratedCompositing()) {
         m_markedCanvasDirty = true;