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

ui/gl/gl_image_stub.cc

Index: ui/gl/gl_image_stub.cc
diff --git a/ui/gl/gl_image_stub.cc b/ui/gl/gl_image_stub.cc
index 6549e890faf9189da86f235c38f8ccb69b229626..afbf6e04178657974d97b67e905a2fff93d22e16 100644
--- a/ui/gl/gl_image_stub.cc
+++ b/ui/gl/gl_image_stub.cc
@@ -18,7 +18,11 @@ unsigned GLImageStub::GetInternalFormat() { return GL_RGBA; }
 
 bool GLImageStub::BindTexImage(unsigned target) { return true; }
 
-bool GLImageStub::CopyTexImage(unsigned target) { return true; }
+bool GLImageStub::CopyTexSubImage(unsigned target,
+                                  const Point& offset,
+                                  const Rect& rect) {
+  return true;
+}
 
 bool GLImageStub::ScheduleOverlayPlane(gfx::AcceleratedWidget widget,
                                        int z_order,