Fix DirectCompositionSurfaceTest.TestMakeCurrent flakiness.

gpu/ipc/service/direct_composition_surface_win.cc

Index: gpu/ipc/service/direct_composition_surface_win.cc
diff --git a/gpu/ipc/service/direct_composition_surface_win.cc b/gpu/ipc/service/direct_composition_surface_win.cc
index 317964e52229a8212250631c6ba69032eba7f4c8..aea60f57a008658f164076b0161d7fe4c542590e 100644
--- a/gpu/ipc/service/direct_composition_surface_win.cc
+++ b/gpu/ipc/service/direct_composition_surface_win.cc
@@ -323,6 +323,11 @@ bool DirectCompositionSurfaceWin::SetDrawRectangle(const gfx::Rect& rectangle) {
   return true;
 }
 
+scoped_refptr<base::TaskRunner>
+DirectCompositionSurfaceWin::GetWindowTaskRunnerForTesting() {
+  return child_window_.GetTaskRunnerForTesting();
+}
+
 DirectCompositionSurfaceWin::Overlay::Overlay(int z_order,
                                               gfx::OverlayTransform transform,
                                               scoped_refptr<gl::GLImage> image,