Uses and returns the fractional width in text eliding

ui/gfx/render_text.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_H_
 #define UI_GFX_RENDER_TEXT_H_
 
 #include <algorithm>
 #include <cstring>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/gtest_prod_util.h"
 #include "base/i18n/rtl.h"
 #include "base/strings/string16.h"
 #include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "third_party/skia/include/core/SkPaint.h"
 #include "third_party/skia/include/core/SkRect.h"
 #include "ui/gfx/break_list.h"
 #include "ui/gfx/font_list.h"
 #include "ui/gfx/point.h"
 #include "ui/gfx/range/range.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/selection_model.h"
 #include "ui/gfx/shadow_value.h"
+#include "ui/gfx/size_f.h"
 #include "ui/gfx/text_constants.h"
 #include "ui/gfx/vector2d.h"
 
 class SkCanvas;
 class SkDrawLooper;
 struct SkPoint;
 class SkShader;
 class SkTypeface;
 
 namespace gfx {
@@ skipping 281 matching lines @@
   // of the text, considering only the dominant direction returned by
   // |GetTextDirection()|, not the direction of a particular run.
   VisualCursorDirection GetVisualDirectionOfLogicalEnd();
 
   // Returns the size required to display the current string (which is the
   // wrapped size in multiline mode). Note that this returns the raw size of the
   // string, which does not include the cursor or the margin area of text
   // shadows.
   virtual Size GetStringSize() = 0;
 
+  // This is same as GetStringSize except that fractional size is returned.
+  // The default implementation is same as GetStringSize. Certain platforms that
+  // compute the text size as floating-point values, like Mac, will override
+  // this method.
+  virtual SizeF GetStringSizeF();
+
   // Returns the width of the content (which is the wrapped width in multiline
   // mode). Reserves room for the cursor if |cursor_enabled_| is true.
   int GetContentWidth();
 
   // Returns the common baseline of the text. The returned value is the vertical
   // offset from the top of |display_rect| to the text baseline, in pixels.
   virtual int GetBaseline() = 0;
 
   void Draw(Canvas* canvas);
 
@@ skipping 297 matching lines @@
   // Lines computed by EnsureLayout. These should be invalidated with
   // ResetLayout and on |display_rect_| changes.
   std::vector<internal::Line> lines_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderText);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_H_