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

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

Index: third_party/WebKit/Source/core/frame/ImageBitmap.cpp
diff --git a/third_party/WebKit/Source/core/frame/ImageBitmap.cpp b/third_party/WebKit/Source/core/frame/ImageBitmap.cpp
index 19d831308e299cff8b57d5825a9bd4400b1ecd03..c394b0bc75337d56900e10bafc95ae29a5fcc473 100644
--- a/third_party/WebKit/Source/core/frame/ImageBitmap.cpp
+++ b/third_party/WebKit/Source/core/frame/ImageBitmap.cpp
@@ -466,6 +466,13 @@ unsigned long ImageBitmap::height() const
     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)