Simply rules for compositing fixed position elements

Source/core/rendering/RenderLayer.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 358 matching lines @@
 
     bool hasFilterInfo() const { return m_hasFilterInfo; }
     void setHasFilterInfo(bool hasFilterInfo) { m_hasFilterInfo = hasFilterInfo; }
 
     void updateFilters(const RenderStyle* oldStyle, const RenderStyle* newStyle);
 
     Node* enclosingElement() const;
 
     bool isInTopLayer() const;
 
-    enum ViewportConstrainedNotCompositedReason {
-        NoNotCompositedReason = 0,
-        NotCompositedForBoundsOutOfView,
-        NotCompositedForNonViewContainer,
-        NotCompositedForNoVisibleContent,
-        NotCompositedForUnscrollableAncestors,
-        NumNotCompositedReasons,
-
-        // This is the number of bits used to store the viewport constrained not composited
-        // reasons. We define this constant since sizeof won't return the number of bits, and we
-        // shouldn't duplicate the constant.
-        ViewportConstrainedNotCompositedReasonBits = 3
-    };
-
-    void setViewportConstrainedNotCompositedReason(ViewportConstrainedNotCompositedReason reason) { m_viewportConstrainedNotCompositedReason = reason; }
-    ViewportConstrainedNotCompositedReason viewportConstrainedNotCompositedReason() const { ASSERT(isAllowedToQueryCompositingState()); return static_cast<ViewportConstrainedNotCompositedReason>(m_viewportConstrainedNotCompositedReason); }
-
     bool scrollsWithViewport() const;
     bool scrollsWithRespectTo(const RenderLayer*) const;
 
     void addLayerHitTestRects(LayerHitTestRects&) const;
 
     // Compute rects only for this layer
     void computeSelfHitTestRects(LayerHitTestRects&) const;
 
     // FIXME: This should probably return a ScrollableArea but a lot of internal methods are mistakenly exposed.
     RenderLayerScrollableArea* scrollableArea() const { return m_scrollableArea.get(); }
@@ skipping 300 matching lines @@
     // as opposed to the tree formed by the z-order and normal flow lists).
     unsigned m_hasNonCompositedChild : 1;
 
     // Should be for stacking contexts having unisolated blending descendants.
     unsigned m_shouldIsolateCompositedDescendants : 1;
 
     // True if this render layer just lost its grouped mapping due to the CompositedLayerMapping being destroyed,
     // and we don't yet know to what graphics layer this RenderLayer will be assigned.
     unsigned m_lostGroupedMapping : 1;
 
-    // The reason, if any exists, that a fixed-position layer is chosen not to be composited.
-    unsigned m_viewportConstrainedNotCompositedReason : ViewportConstrainedNotCompositedReasonBits;
-
     RenderLayerModelObject* m_renderer;
 
     RenderLayer* m_parent;
     RenderLayer* m_previous;
     RenderLayer* m_next;
     RenderLayer* m_first;
     RenderLayer* m_last;
 
     // Our current relative position offset.
     LayoutSize m_offsetForInFlowPosition;
@@ skipping 41 matching lines @@
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLayerTree(const blink::RenderLayer*);
 void showLayerTree(const blink::RenderObject*);
 #endif
 
 #endif // RenderLayer_h