ui: Add sub region copy support to GLImage::CopyTexImage.

ui/gl/gl_image_io_surface.cc

Index: ui/gl/gl_image_io_surface.cc
diff --git a/ui/gl/gl_image_io_surface.cc b/ui/gl/gl_image_io_surface.cc
index 3c4658d7bd91c291aaaf0cecf17a68dafc874bbe..f8a773c544a36a0aab461b2f4eef273f2254a4b8 100644
--- a/ui/gl/gl_image_io_surface.cc
+++ b/ui/gl/gl_image_io_surface.cc
@@ -177,7 +177,9 @@ bool GLImageIOSurface::BindTexImage(unsigned target) {
   return true;
 }
 
-bool GLImageIOSurface::CopyTexImage(unsigned target) {
+bool GLImageIOSurface::CopyTexSubImage(unsigned target,
+                                       const Point& offset,
+                                       const Rect& rect) {
   return false;
 }