[css-grid] Fix 1% regression on system_health.memory_desktop

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 1985 matching lines @@
     for (size_t i = shadowList->shadows().size(); i--; ) {
         if (shadowList->shadows()[i].color().isCurrentColor())
             return true;
     }
     return false;
 }
 
 static inline Vector<GridTrackSize> initialGridAutoTracks()
 {
     Vector<GridTrackSize> trackSizeList;
-    trackSizeList.append(GridTrackSize(Length(Auto)));
+    trackSizeList.reserveInitialCapacity(1);

[jfernandez, 2016/08/30 11:05:13]

Wouldn't make more sense to pay with Vector's inlineCapacity ? We may get
performance improvements by setting an adjusted inlineCapacity value if we knoe
the vector is going to be small.  Not really sure about the exact value, though.

+    trackSizeList.uncheckedAppend(GridTrackSize(Length(Auto)));
     return trackSizeList;
 }
 
 Vector<GridTrackSize> ComputedStyle::initialGridAutoColumns()
 {
     return initialGridAutoTracks();
 }
 
 Vector<GridTrackSize> ComputedStyle::initialGridAutoRows()
 {
@@ skipping 10 matching lines @@
         if (value < 0)
             fvalue -= 0.5f;
         else
             fvalue += 0.5f;
     }
 
     return roundForImpreciseConversion<int>(fvalue / zoomFactor);
 }
 
 } // namespace blink