Reland of Revert of gpu: introduce glCopySubTextureCHROMIUM (patchset #1 id:1 of https://codereview…

ui/gl/gl_image.h

Index: ui/gl/gl_image.h
diff --git a/ui/gl/gl_image.h b/ui/gl/gl_image.h
index 214241396becbf60949ed713278eb9ee3323c782..289ec60226df4dc526ac9f578f09cfc873406279 100644
--- a/ui/gl/gl_image.h
+++ b/ui/gl/gl_image.h
@@ -33,8 +33,8 @@ class GL_EXPORT GLImage : public base::RefCounted<GLImage> {
   // Release image from texture currently bound to |target|.
   virtual void ReleaseTexImage(unsigned target) = 0;
 
-  // Copy image to texture currently bound to |target|.
-  virtual bool CopyTexImage(unsigned target) = 0;
+  // Copy subimage to texture currently bound to |target|.
+  virtual bool CopyTexSubImage(unsigned target, int xoffset, int yoffset) = 0;

[reveman, 2015/03/04 20:56:46]

We don't really need xoffset and yoffset for this optimization. Can we just keep
this as it is and not call this function if offsets are non-zero?

[dshwang, 2015/03/04 21:02:15]

Indeed. However, implementation can handle offsets.
Anyway as you want, I'll rollback this change to as-is

 
   // Called before the texture is used for drawing.
   virtual void WillUseTexImage() = 0;