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

ui/gfx/platform_font_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_PLATFORM_FONT_MAC_H_
 #define UI_GFX_PLATFORM_FONT_MAC_H_
 
 #include "base/compiler_specific.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/macros.h"
 #include "ui/gfx/font_render_params.h"
 #include "ui/gfx/platform_font.h"
 
 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);
 
   // Overridden from PlatformFont:
   Font DeriveFont(int size_delta,
                   int style,
                   Font::Weight weight) const override;
   int GetHeight() override;
   Font::Weight GetWeight() const override;
   int GetBaseline() override;
@@ skipping 37 matching lines @@
 
   // Details about how the font should be rendered.
   FontRenderParams render_params_;
 
   DISALLOW_COPY_AND_ASSIGN(PlatformFontMac);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_PLATFORM_FONT_MAC_H_