2D canvas: remain in deferred rendering mode with canvas to canvas drawImage

Source/modules/canvas2d/CanvasRenderingContext2D.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008 Dirk Schulze <krit@webkit.org>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  * Copyright (C) 2012, 2013 Intel Corporation. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
@@ skipping 1335 matching lines @@
         c->translate(dstRect.x(), dstRect.y());
         c->scale(dstRect.width() / srcRect.width(), dstRect.height() / srcRect.height());
         c->translate(-srcRect.x(), -srcRect.y());
         HTMLVideoElement* video = static_cast<HTMLVideoElement*>(imageSource);
         video->paintCurrentFrame(c, IntRect(IntPoint(), IntSize(video->videoWidth(), video->videoHeight())), &imagePaint);
     }
 
     c->restoreToCount(initialSaveCount);
 }
 
+bool shouldDisableDeferral(CanvasImageSource* imageSource)
+{
+    if (imageSource->isVideoElement())
+        return true;
+    if (imageSource->isCanvasElement()) {
+        HTMLCanvasElement* canvas = static_cast<HTMLCanvasElement*>(imageSource);
+        if (canvas->is3D())
+            return true;
+        if (canvas->isAnimated2D())
+            return true;
+    }
+    return false;
+}
+
 void CanvasRenderingContext2D::drawImage(CanvasImageSource* imageSource,
     float sx, float sy, float sw, float sh,
     float dx, float dy, float dw, float dh, ExceptionState& exceptionState)
 {
     if (!drawingCanvas())
         return;
 
     RefPtr<Image> image;
     SourceImageStatus sourceImageStatus = InvalidSourceImageStatus;
     if (!imageSource->isVideoElement()) {
@@ skipping 15 matching lines @@
     FloatRect srcRect = normalizeRect(FloatRect(sx, sy, sw, sh));
     FloatRect dstRect = normalizeRect(FloatRect(dx, dy, dw, dh));
 
     clipRectsToImageRect(FloatRect(FloatPoint(), imageSource->elementSize()), &srcRect, &dstRect);
 
     imageSource->adjustDrawRects(&srcRect, &dstRect);
 
     if (srcRect.isEmpty())
         return;
 
-    // FIXME: crbug.com/521001
-    // We make the destination canvas fall out of display list mode by forcing
-    // immediate rendering. This is to prevent run-away memory consumption caused by SkSurface
-    // copyOnWrite when the source canvas is animated and consumed at a rate higher than the
-    // presentation frame rate of the destination canvas.
-    if (imageSource->isVideoElement() || imageSource->isCanvasElement())
+    if (shouldDisableDeferral(imageSource))
         canvas()->disableDeferral();
 
     validateStateStack();
 
     draw(
         [this, &imageSource, &image, &srcRect, dstRect](SkCanvas* c, const SkPaint* paint) // draw lambda
         {
             drawImageInternal(c, imageSource, image.get(), srcRect, dstRect, paint);
         },
         [this, &dstRect](const SkIRect& clipBounds) // overdraw test lambda
@@ skipping 904 matching lines @@
         if (imageType == CanvasRenderingContext2DState::NonOpaqueImage)
             return;
         if (alpha < 0xFF)
             return;
     }
 
     canvas()->buffer()->willOverwriteCanvas();
 }
 
 } // namespace blink