ui/gfx: Use base::string16 now that string16 was moved into base namespace.

ui/gfx/platform_font_pango.cc

Index: ui/gfx/platform_font_pango.cc
diff --git a/ui/gfx/platform_font_pango.cc b/ui/gfx/platform_font_pango.cc
index dcdbde74e0fbeee159f9a98b9f22e8d5e5ea7b7f..b950d23aac1462fe1db3273d3dc16650f9fd3989 100644
--- a/ui/gfx/platform_font_pango.cc
+++ b/ui/gfx/platform_font_pango.cc
@@ -198,7 +198,7 @@ int PlatformFontPango::GetAverageCharacterWidth() const {
   return SkScalarRound(average_width_pixels_);
 }
 
-int PlatformFontPango::GetStringWidth(const string16& text) const {
+int PlatformFontPango::GetStringWidth(const base::string16& text) const {
   return Canvas::GetStringWidth(text,
                                 Font(const_cast<PlatformFontPango*>(this)));
 }