Mac: Fix PlatformFontMac::DeriveFont for underline font style.

ui/gfx/platform_font_mac.h

Index: ui/gfx/platform_font_mac.h
diff --git a/ui/gfx/platform_font_mac.h b/ui/gfx/platform_font_mac.h
index 63a0cbd2bbf05d8aa94ea46e661d77a13df3212e..682f88bd383df5825412f01807a5209f5e7e27e3 100644
--- a/ui/gfx/platform_font_mac.h
+++ b/ui/gfx/platform_font_mac.h
@@ -16,7 +16,7 @@ namespace gfx {
 class PlatformFontMac : public PlatformFont {
  public:
   PlatformFontMac();
-  explicit PlatformFontMac(NativeFont native_font);
+  explicit PlatformFontMac(NativeFont native_font, bool underline = false);

[Avi (use Gerrit), 2016/08/05 14:54:59]

If you have two parameters, you don't need to have this marked "explicit" any
more.

   PlatformFontMac(const std::string& font_name,
                   int font_size);