Snap inline box boundaries to layout units during line breaking.

third_party/WebKit/Source/core/layout/line/LineWidth.h

Index: third_party/WebKit/Source/core/layout/line/LineWidth.h
diff --git a/third_party/WebKit/Source/core/layout/line/LineWidth.h b/third_party/WebKit/Source/core/layout/line/LineWidth.h
index 2db3736d6cb6e073958ae4eafd213a5df11e4daf..89fca11d2ef08692111c35649af29490169109e2 100644
--- a/third_party/WebKit/Source/core/layout/line/LineWidth.h
+++ b/third_party/WebKit/Source/core/layout/line/LineWidth.h
@@ -54,7 +54,11 @@ public:
         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; }
@@ -68,6 +72,7 @@ public:
     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; }