Snap inline box boundaries to layout units during line breaking.

third_party/WebKit/Source/core/layout/line/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 36 matching lines @@
 public:
     LineWidth(LineLayoutBlockFlow, bool isFirstLine, IndentTextOrNot shouldIndentText);
 
     bool fitsOnLine() const { return currentWidth() <= (m_availableWidth + LayoutUnit::epsilon()); }
     bool fitsOnLine(float extra) const { return currentWidth() + extra <= (m_availableWidth + LayoutUnit::epsilon()); }
     bool fitsOnLine(float extra, WhitespaceTreatment whitespaceTreatment) const
     {
         return currentWidth() - (whitespaceTreatment == ExcludeWhitespace ? trailingWhitespaceWidth() : 0) + extra <= (m_availableWidth + LayoutUnit::epsilon());
     }
 
+    // Note that m_uncommittedWidth may not be LayoutUnit-snapped at this point.  Because
+    // currentWidth() is used by the code that lays out words in a single LayoutText, it's
+    // expected that offsets will not be snapped until an InlineBox boundary is reached.
     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; }
     float trailingWhitespaceWidth() const { return m_trailingWhitespaceWidth; }
 
     void updateAvailableWidth(LayoutUnit minimumHeight = 0);
     void shrinkAvailableWidthForNewFloatIfNeeded(const FloatingObject&);
     void addUncommittedWidth(float delta) { m_uncommittedWidth += delta; }
     void commit();
     void applyOverhang(LineLayoutRubyRun, LineLayoutItem startLayoutItem, LineLayoutItem endLayoutItem);
     void fitBelowFloats(bool isFirstLine = false);
     void setTrailingWhitespaceWidth(float width) { m_trailingWhitespaceWidth = width; }
+    void snapUncommittedWidth() { m_uncommittedWidth = LayoutUnit(m_uncommittedWidth).toFloat(); }
 
     bool shouldIndentText() const { return m_shouldIndentText == IndentText; }
 
 private:
     void computeAvailableWidthFromLeftAndRight();
     void updateLineDimension(LayoutUnit newLineTop, LayoutUnit newLineWidth, const float& newLineLeft, const float& newLineRight);
     void wrapNextToShapeOutside(bool isFirstLine);
 
     LineLayoutBlockFlow m_block;
     float m_uncommittedWidth;
     float m_committedWidth;
     float m_overhangWidth; // The amount by which |m_availableWidth| has been inflated to account for possible contraction due to ruby overhang.
     float m_trailingWhitespaceWidth;
     float m_left;
     float m_right;
     float m_availableWidth;
     bool m_isFirstLine;
     IndentTextOrNot m_shouldIndentText;
 };
 
 }
 
 #endif // LineWidth_h