Force flattening for elements with non-initial value of opacity

third_party/WebKit/Source/core/style/ComputedStyle.cpp

 /*
  * Copyright (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 1241 matching lines @@
     return *rareNonInheritedData->m_animations;
 }
 
 CSSTransitionData& ComputedStyle::accessTransitions()
 {
     if (!rareNonInheritedData.access()->m_transitions)
         rareNonInheritedData.access()->m_transitions = CSSTransitionData::create();
     return *rareNonInheritedData->m_transitions;
 }
 
+ETransformStyle3D ComputedStyle::usedTransformStyle3D() const
+{
+    // Quick rejection. Technically no-op.
+    if (transformStyle3D() == TransformStyle3DFlat)

[chrishtr, 2016/06/15 16:06:41]

Does this really matter for performance?

[trchen, 2016/06/18 00:27:09]

I don't have numbers, but checking will-change list can be potentially
expensive.

[chrishtr, 2016/06/18 08:22:53]

All this saves is a call to hasGroupingProperty. I don't think it's worth it.

+        return TransformStyle3DFlat;
+
+    return hasGroupingProperty() ? TransformStyle3DFlat : transformStyle3D();
+}
+
 const Font& ComputedStyle::font() const { return inherited->font; }
 const FontMetrics& ComputedStyle::getFontMetrics() const { return inherited->font.getFontMetrics(); }
 const FontDescription& ComputedStyle::getFontDescription() const { return inherited->font.getFontDescription(); }
 float ComputedStyle::specifiedFontSize() const { return getFontDescription().specifiedSize(); }
 float ComputedStyle::computedFontSize() const { return getFontDescription().computedSize(); }
 int ComputedStyle::fontSize() const { return getFontDescription().computedPixelSize(); }
 float ComputedStyle::fontSizeAdjust() const { return getFontDescription().sizeAdjust(); }
 bool ComputedStyle::hasFontSizeAdjust() const { return getFontDescription().hasSizeAdjust(); }
 FontWeight ComputedStyle::fontWeight() const { return getFontDescription().weight(); }
 FontStretch ComputedStyle::fontStretch() const { return getFontDescription().stretch(); }
@@ skipping 601 matching lines @@
         if (value < 0)
             fvalue -= 0.5f;
         else
             fvalue += 0.5f;
     }
 
     return roundForImpreciseConversion<int>(fvalue / zoomFactor);
 }
 
 } // namespace blink