Uses and returns the fractional width in text eliding

ui/gfx/render_text_mac.h

Index: ui/gfx/render_text_mac.h
diff --git a/ui/gfx/render_text_mac.h b/ui/gfx/render_text_mac.h
index be5f12865c0c5c0734c8b526d26cc9742146d727..3d25430b8fe08378526f64994814527aa74cec28 100644
--- a/ui/gfx/render_text_mac.h
+++ b/ui/gfx/render_text_mac.h
@@ -27,6 +27,7 @@ class RenderTextMac : public RenderText {
 
   // Overridden from RenderText:
   virtual Size GetStringSize() OVERRIDE;
+  virtual SizeF GetStringSizeF() OVERRIDE;
   virtual int GetBaseline() OVERRIDE;
   virtual SelectionModel FindCursorPosition(const Point& point) OVERRIDE;
   virtual std::vector<FontSpan> GetFontSpansForTesting() OVERRIDE;
@@ -81,7 +82,7 @@ class RenderTextMac : public RenderText {
   base::ScopedCFTypeRef<CFMutableArrayRef> attributes_;
 
   // Visual dimensions of the text. Computed by |EnsureLayout()|.
-  Size string_size_;
+  SizeF string_size_;
 
   // Common baseline for this line of text. Computed by |EnsureLayout()|.
   SkScalar common_baseline_;