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

ui/gl/gl_image_surface_texture.cc

Index: ui/gl/gl_image_surface_texture.cc
diff --git a/ui/gl/gl_image_surface_texture.cc b/ui/gl/gl_image_surface_texture.cc
index 1fcb0fcaacd7789c9aecc6add816bfef80fc642b..bec06be8f242d8e227cdc50cd8082e0b64af6890 100644
--- a/ui/gl/gl_image_surface_texture.cc
+++ b/ui/gl/gl_image_surface_texture.cc
@@ -78,7 +78,9 @@ bool GLImageSurfaceTexture::BindTexImage(unsigned target) {
   return true;
 }
 
-bool GLImageSurfaceTexture::CopyTexImage(unsigned target) {
+bool GLImageSurfaceTexture::CopyTexSubImage(unsigned target,
+                                            const Point& offset,
+                                            const Rect& rect) {
   return false;
 }