Don't submit frames with no render passes in cc tests

cc/test/compositor_frame_helpers.h

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_TEST_COMPOSITOR_FRAME_HELPERS_H_
 #define CC_TEST_COMPOSITOR_FRAME_HELPERS_H_
 
 namespace cc {
 
 class CompositorFrame;
 
 namespace test {
 
+// Creates a valid CompositorFrame.
 CompositorFrame MakeCompositorFrame();
 
+// Creates a CompositorFrame that will be valid once its render_pass_list is
+// initialized.
+CompositorFrame MakeEmptyCompositorFrame();
+
 }  // namespace test
 }  // namespace cc
 
 #endif  // CC_TEST_COMPOSITOR_FRAME_HELPERS_H_