compositor-worker: Initialize CW machinery plumbing to compositor and fire CW rAF callbacks.

third_party/WebKit/Source/platform/graphics/CompositorMutator.h

+// Copyright 2016 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 CompositorMutator_h
+#define CompositorMutator_h
+
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class CompositorMutator : public GarbageCollectedMixin {
+public:
+    DEFINE_INLINE_VIRTUAL_TRACE() {}
+
+    // Called from compositor thread to run the animation frame callbacks from all
+    // connected CompositorWorkers.
+    // Returns true if any animation callbacks requested an animation frame
+    // (i.e. should be reinvoked next frame).
+    virtual bool mutate(double monotonicTimeNow) = 0;
+};
+
+} // namespace blink
+
+#endif // CompositorMutator_h