Fix DirectCompositionSurfaceTest.TestMakeCurrent flakiness.

gpu/ipc/service/child_window_win.h

Index: gpu/ipc/service/child_window_win.h
diff --git a/gpu/ipc/service/child_window_win.h b/gpu/ipc/service/child_window_win.h
index 2bccf9ff926e310c77fef88b795ab3b8811474f3..c11202b12da8fc540a78c3b13f731fc33d2d63b3 100644
--- a/gpu/ipc/service/child_window_win.h
+++ b/gpu/ipc/service/child_window_win.h
@@ -6,6 +6,7 @@
 #define GPU_IPC_SERVICE_CHILD_WINDOW_WIN_H_
 
 #include "base/memory/weak_ptr.h"
+#include "base/task_runner.h"
 #include "gpu/ipc/service/image_transport_surface_delegate.h"
 
 #include <windows.h>
@@ -27,6 +28,8 @@ class ChildWindowWin {
   void ClearInvalidContents();
   HWND window() const { return window_; }
 
+  scoped_refptr<base::TaskRunner> GetTaskRunnerForTesting();
+
  private:
   // This member contains all the data that can be accessed from the main or
   // window owner threads.