Uses and returns the fractional width in text eliding

ui/gfx/render_text_mac.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_GFX_RENDER_TEXT_MAC_H_
 #define UI_GFX_RENDER_TEXT_MAC_H_
 
 #include <ApplicationServices/ApplicationServices.h>
 
 #include <string>
 #include <vector>
 
 #include "base/mac/scoped_cftyperef.h"
 #include "ui/gfx/render_text.h"
 
 namespace gfx {
 
 // RenderTextMac is the Mac implementation of RenderText that uses CoreText for
 // layout and Skia for drawing.
 //
 // Note: The current implementation only supports drawing and sizing the text,
 //       but not text selection or cursor movement.
 class RenderTextMac : public RenderText {
  public:
   RenderTextMac();
   virtual ~RenderTextMac();
 
   // 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;
 
  protected:
   // Overridden from RenderText:
   virtual SelectionModel AdjacentCharSelectionModel(
       const SelectionModel& selection,
       VisualCursorDirection direction) OVERRIDE;
   virtual SelectionModel AdjacentWordSelectionModel(
@@ skipping 34 matching lines @@
   void ComputeRuns();
 
   // The Core Text line of text. Created by |EnsureLayout()|.
   base::ScopedCFTypeRef<CTLineRef> line_;
 
   // Array to hold CFAttributedString attributes that allows Core Text to hold
   // weak references to them without leaking.
   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_;
 
   // Visual text runs. Only valid if |runs_valid_| is true. Computed by
   // |ComputeRuns()|.
   std::vector<TextRun> runs_;
 
   // Indicates that |runs_| are valid, set by |ComputeRuns()|.
   bool runs_valid_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderTextMac);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_MAC_H_