Revert "Make compositingState explicit (re-land #2 with bogus ASSERT removed)"

Source/core/rendering/CompositingState.h

-// 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.
-
-#ifndef CompositingState_h
-#define CompositingState_h
-
-namespace WebCore {
-
-enum CompositingState {
-    // The layer paints into its enclosing composited ancestor.
-    NotComposited = 0,
-
-    // The layer is composited, but its contents still paint into enclosing composited ancestor.
-    // In this state, repaint invalidations must be sent to the enclosing composited ancestor.
-    // Typically this happens when a layer's properties need to be represented in the compositor
-    // output data structures, but it doesn't actually have any other reasons to be composited.
-    HasOwnBackingButPaintsIntoAncestor = 1,
-
-    PaintsIntoOwnBacking = 2,
-};
-
-} // namespace WebCore
-
-#endif // CompositingState_h