Use views::style for buttons, bootstrap ash_typography to do so.

chrome/browser/ui/views/harmony/chrome_typography.cc

 // Copyright 2017 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.
 
 #include "chrome/browser/ui/views/harmony/chrome_typography.h"
 
 #include "ui/base/default_style.h"
 #include "ui/base/resource/resource_bundle.h"
 
 const gfx::FontList& LegacyTypographyProvider::GetFont(int text_context,
                                                        int text_style) const {
   constexpr int kHeadlineDelta = 8;
   constexpr int kDialogMessageDelta = 1;
 
   int size_delta;
   gfx::Font::Weight font_weight;
   GetDefaultFont(text_context, text_style, &size_delta, &font_weight);
 
+#if defined(USE_ASH)
+  ash::ApplyAshFontStyles(text_context, text_style, &size_delta, &font_weight);
+#endif
+
   switch (text_context) {
     case CONTEXT_HEADLINE:
       size_delta = kHeadlineDelta;
       break;
     case CONTEXT_BODY_TEXT_LARGE:
       // Note: Not using ui::kMessageFontSizeDelta, so 13pt in most cases.
       size_delta = kDialogMessageDelta;
       break;
     case CONTEXT_BODY_TEXT_SMALL:
       size_delta = ui::kLabelFontSizeDelta;
       break;
     case CONTEXT_DEPRECATED_SMALL:
       size_delta = ui::ResourceBundle::kSmallFontDelta;
       break;
   }
 
   switch (text_style) {
     case STYLE_EMPHASIZED:
       font_weight = gfx::Font::Weight::BOLD;
       break;
   }
   constexpr gfx::Font::FontStyle kFontStyle = gfx::Font::NORMAL;
   return ui::ResourceBundle::GetSharedInstance().GetFontListWithDelta(
       size_delta, kFontStyle, font_weight);
 }