Skip PaintPhaseFloat if no floats in a layer

third_party/WebKit/Source/core/paint/PaintLayer.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 608 matching lines @@
 
     LayoutRect previousPaintDirtyRect() const { return m_previousPaintDirtyRect; }
     void setPreviousPaintDirtyRect(const LayoutRect& rect) { m_previousPaintDirtyRect = rect; }
 
     PaintLayerPainter::PaintResult previousPaintResult() const { return static_cast<PaintLayerPainter::PaintResult>(m_previousPaintResult); }
     void setPreviousPaintResult(PaintLayerPainter::PaintResult result) { m_previousPaintResult = static_cast<unsigned>(result); ASSERT(m_previousPaintResult == static_cast<unsigned>(result)); }
 
     bool needsPaintPhaseDescendantOutlines() const { return m_needsPaintPhaseDescendantOutlines; }
     void setNeedsPaintPhaseDescendantOutlines() { ASSERT(isSelfPaintingLayer()); m_needsPaintPhaseDescendantOutlines = true; }
 
+    bool needsPaintPhaseFloat() const { return m_needsPaintPhaseFloat; }

[chrishtr, 2016/01/22 00:14:44]

Add a comment that once-float, always float.

[Xianzhu, 2016/01/22 00:50:24]

Added full comments in https://codereview.chromium.org/1584493002/ for
descendant outlines above, and add comment for this method referencing above.

+    void setNeedsPaintPhaseFloat() { ASSERT(isSelfPaintingLayer()); m_needsPaintPhaseFloat = true; }
+
     PaintTiming* paintTiming();
 
 private:
     // Bounding box in the coordinates of this layer.
     LayoutRect logicalBoundingBox() const;
 
     bool hasOverflowControls() const;
 
     void dirtyAncestorChainHasSelfPaintingLayerDescendantStatus();
 
@@ skipping 113 matching lines @@
     unsigned m_shouldIsolateCompositedDescendants : 1;
 
     // True if this layout layer just lost its grouped mapping due to the CompositedLayerMapping being destroyed,
     // and we don't yet know to what graphics layer this Layer will be assigned.
     unsigned m_lostGroupedMapping : 1;
 
     unsigned m_needsRepaint : 1;
     unsigned m_previousPaintResult : 1; // PaintLayerPainter::PaintResult
 
     unsigned m_needsPaintPhaseDescendantOutlines : 1;
+    unsigned m_needsPaintPhaseFloat : 1;
 
     LayoutBoxModelObject* m_layoutObject;
 
     PaintLayer* m_parent;
     PaintLayer* m_previous;
     PaintLayer* m_next;
     PaintLayer* m_first;
     PaintLayer* m_last;
 
     // Our current relative position offset.
@@ skipping 54 matching lines @@
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLayerTree(const blink::PaintLayer*);
 void showLayerTree(const blink::LayoutObject*);
 #endif
 
 #endif // Layer_h