Enable experimental support for sub-pixel font scaling

Source/core/rendering/LineWidth.h

 /*
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
  *    disclaimer.
@@ skipping 30 matching lines @@
 class RenderBlockFlow;
 
 struct LineSegment;
 
 enum IndentTextOrNot { DoNotIndentText, IndentText };
 
 class LineWidth {
 public:
     LineWidth(RenderBlockFlow&, bool isFirstLine, IndentTextOrNot shouldIndentText);
 
-    bool fitsOnLine() const { return currentWidth() <= m_availableWidth; }
-    bool fitsOnLine(float extra) const { return currentWidth() + extra <= m_availableWidth; }
+    bool fitsOnLine() const { return currentWidth() <= (m_availableWidth + LayoutUnit::epsilon()); }
+    bool fitsOnLine(float extra) const { return currentWidth() + extra <= (m_availableWidth + LayoutUnit::epsilon()); }
 
     float currentWidth() const { return m_committedWidth + m_uncommittedWidth; }
     // FIXME: We should eventually replace these three functions by ones that work on a higher abstraction.
     float uncommittedWidth() const { return m_uncommittedWidth; }
     float committedWidth() const { return m_committedWidth; }
     float availableWidth() const { return m_availableWidth; }
 
     void updateAvailableWidth(LayoutUnit minimumHeight = 0);
     void shrinkAvailableWidthForNewFloatIfNeeded(FloatingObject*);
     void addUncommittedWidth(float delta) { m_uncommittedWidth += delta; }
@@ skipping 16 matching lines @@
     float m_right;
     float m_availableWidth;
     const LineSegment* m_segment;
     bool m_isFirstLine;
     IndentTextOrNot m_shouldIndentText;
 };
 
 }
 
 #endif // LineWidth_h