Uses and returns the fractional width in text eliding

ui/gfx/platform_font_mac.mm

Index: ui/gfx/platform_font_mac.mm
diff --git a/ui/gfx/platform_font_mac.mm b/ui/gfx/platform_font_mac.mm
index bf0c0bd54acaaf13d5928942cd8a169b69a47d63..18a4044f3b960945c7ef3a54c33b51ada933d574 100644
--- a/ui/gfx/platform_font_mac.mm
+++ b/ui/gfx/platform_font_mac.mm
@@ -59,16 +59,16 @@ int PlatformFontMac::GetBaseline() const {
   return ascent_;
 }
 
-int PlatformFontMac::GetAverageCharacterWidth() const {
+float PlatformFontMac::GetAverageCharacterWidth() const {
   return average_width_;
 }
 
-int PlatformFontMac::GetStringWidth(const base::string16& text) const {
+float PlatformFontMac::GetStringWidth(const base::string16& text) const {
   return Canvas::GetStringWidth(text,
                                 Font(const_cast<PlatformFontMac*>(this)));
 }
 
-int PlatformFontMac::GetExpectedTextWidth(int length) const {
+float PlatformFontMac::GetExpectedTextWidth(int length) const {
   return length * average_width_;
 }