Avoid GPU readback in tex(Sub)Image2D(ImageBitmap)

third_party/WebKit/Source/core/frame/ImageBitmap.cpp

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/frame/ImageBitmap.h"
 
 #include "core/html/HTMLCanvasElement.h"
 #include "core/html/HTMLVideoElement.h"
 #include "core/html/ImageData.h"
 #include "platform/graphics/skia/SkiaUtils.h"
@@ skipping 448 matching lines @@
 }
 
 unsigned long ImageBitmap::height() const
 {
     if (!m_image)
         return 0;
     ASSERT(m_image->height() > 0);
     return m_image->height();
 }
 
+// This function is used in WebGL's texImage, if it returns true, WebGL will a

[Justin Novosad, 2016/06/09 20:21:29]

"will do a"

[xidachen, 2016/06/10 15:36:08]

Done.

+// GPU-GPU texture copy. So this function returns true only when it has a mailbox.
+bool ImageBitmap::isTextureBacked() const
+{
+    return m_image && m_image->hasMailbox();

[Justin Novosad, 2016/06/09 20:21:29]

What about the case where we have no mailbox, but the image is from an
accelerated 2D canvas (and thus has a texture backed SkImage)?  If it is your
intent to ignore that case, then the method should be called something else
(hasMailbox?) to prevent it from being misused or misinterpreted by others.

[xidachen, 2016/06/10 15:36:08]

Changed the implementation to indicate whether bitmap is actually texture backed
or not.

+}
+
 IntSize ImageBitmap::size() const
 {
     if (!m_image)
         return IntSize();
     ASSERT(m_image->width() > 0 && m_image->height() > 0);
     return IntSize(m_image->width(), m_image->height());
 }
 
 ScriptPromise ImageBitmap::createImageBitmap(ScriptState* scriptState, EventTarget& eventTarget, int sx, int sy, int sw, int sh, const ImageBitmapOptions& options, ExceptionState& exceptionState)
 {
@@ skipping 33 matching lines @@
 FloatSize ImageBitmap::elementSize(const FloatSize&) const
 {
     return FloatSize(width(), height());
 }
 
 DEFINE_TRACE(ImageBitmap)
 {
 }
 
 } // namespace blink