DCHECK if shader compilation fails that it's due to context loss.

cc/test/test_context_support.cc

 // Copyright 2013 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.
 
 #include "cc/test/test_context_support.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
 #include "base/thread_task_runner_handle.h"
@@ skipping 69 matching lines @@
     const gfx::RectF& uv_rect) {
   if (!schedule_overlay_plane_callback_.is_null()) {
     schedule_overlay_plane_callback_.Run(plane_z_order,
                                          plane_transform,
                                          overlay_texture_id,
                                          display_bounds,
                                          uv_rect);
   }
 }
 
+bool TestContextSupport::IsContextLost() {
+  return false;
+}
+
 }  // namespace cc