cc: Add finch feature flag for checker-imaging.

cc/base/features.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_BASE_FEATURES_H_
+#define CC_BASE_FEATURES_H_
+
+#include "base/feature_list.h"
+#include "cc/base/base_export.h"
+
+namespace cc {
+namespace features {
+
+CC_BASE_EXPORT extern const base::Feature kEnableCheckerImaging;

[piman, 2017/05/24 18:59:11]

Is this something that belongs in CC - that is, is it something that we would
turn on/off at the same time in every single compositor in existence (in
particular, UI vs renderer compositor). Typically these kind of features are
not, and so they are activated via the LayerTreeSettings.

In particular for this one, I don't think it ever makes sense to checker images
in the UI, so I think we should make it a LayerTreeSetting and the feature would
belong in content, and apply to the renderer only.

[Khushal, 2017/05/24 20:45:07]

Yeah, its only for the renderer compositor. And the activation would happen
using layer tree settings in RenderWidgetCompositor. That's how its being done
already. I just changed it so we plumb it to the renderer based on the finch
config using compositor command line flags appended in RenderProcessHostImpl.

I wasn't sure where I should put the finch feature. Moved it to content_features
since that makes more sense.

+
+}  // namespace features
+}  // namespace cc
+
+#endif  // CC_BASE_FEATURES_H_