Offset scissor and viewport when using SetDrawRectangle on surface.

ui/gl/gl_surface.cc

Index: ui/gl/gl_surface.cc
diff --git a/ui/gl/gl_surface.cc b/ui/gl/gl_surface.cc
index c0ac7f013cd4fcdc09ec0ccbb6eab08a0e89d226..9bddfd3314750e54154574eda5581a668a0d7dfc 100644
--- a/ui/gl/gl_surface.cc
+++ b/ui/gl/gl_surface.cc
@@ -176,6 +176,10 @@ bool GLSurface::SetDrawRectangle(const gfx::Rect& rect) {
   return false;
 }
 
+gfx::Vector2d GLSurface::GetDrawOffset() const {
+  return gfx::Vector2d();
+}
+
 GLSurface* GLSurface::GetCurrent() {
   return current_surface_.Pointer()->Get();
 }
@@ -365,6 +369,10 @@ bool GLSurfaceAdapter::SetDrawRectangle(const gfx::Rect& rect) {
   return surface_->SetDrawRectangle(rect);
 }
 
+gfx::Vector2d GLSurfaceAdapter::GetDrawOffset() const {
+  return surface_->GetDrawOffset();
+}
+
 void GLSurfaceAdapter::OnSetSwapInterval(int interval) {
   surface_->OnSetSwapInterval(interval);
 }