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

ui/views/style/typography_provider.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 "ui/views/style/typography_provider.h"
 
 #include "base/logging.h"
 #include "ui/base/default_style.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/views/style/typography.h"
 
+using gfx::Font;
+
 namespace views {
+namespace {
+
+Font::Weight GetValueBolderThan(Font::Weight weight) {
+  switch (weight) {
+    case Font::Weight::BOLD:
+      return Font::Weight::EXTRA_BOLD;
+    case Font::Weight::EXTRA_BOLD:
+    case Font::Weight::BLACK:
+      return Font::Weight::BLACK;
+    default:
+      return Font::Weight::BOLD;
+  }
+}
+
+}  // namespace
+
+// static
+Font::Weight TypographyProvider::WeightNotLighterThanNormal(
+    Font::Weight weight) {
+  if (ResourceBundle::GetSharedInstance()
+          .GetFontListWithDelta(0, Font::NORMAL, Font::Weight::NORMAL)
+          .GetFontWeight() < weight)
+    return weight;
+  return Font::Weight::NORMAL;
+}
 
 const gfx::FontList& DefaultTypographyProvider::GetFont(int context,
                                                         int style) const {
   int size_delta;
-  gfx::Font::Weight font_weight;
+  Font::Weight font_weight;
   GetDefaultFont(context, style, &size_delta, &font_weight);
   return ResourceBundle::GetSharedInstance().GetFontListWithDelta(
-      size_delta, gfx::Font::NORMAL, font_weight);
+      size_delta, Font::NORMAL, font_weight);
 }
 
-void DefaultTypographyProvider::GetDefaultFont(
-    int context,
-    int style,
-    int* size_delta,
-    gfx::Font::Weight* font_weight) const {
+SkColor DefaultTypographyProvider::GetColor(int context, int style) const {
+  return SK_ColorBLACK;
+}
+
+int DefaultTypographyProvider::GetLineHeight(int context, int style) const {
+  return 0;
+}
+
+// static
+void DefaultTypographyProvider::GetDefaultFont(int context,
+                                               int style,
+                                               int* size_delta,
+                                               Font::Weight* font_weight) {
+  *font_weight = Font::Weight::NORMAL;
+
   switch (context) {
+    case style::CONTEXT_BUTTON_MD:
+      *size_delta = ui::kLabelFontSizeDelta;
+      *font_weight = WeightNotLighterThanNormal(Font::Weight::MEDIUM);
+      break;
     case style::CONTEXT_DIALOG_TITLE:
       *size_delta = ui::kTitleFontSizeDelta;
       break;
+    case style::CONTEXT_TOUCH_MENU:
+      *size_delta = -1;
+      break;
     default:
       *size_delta = ui::kLabelFontSizeDelta;
       break;
   }
 
   switch (style) {
     case style::STYLE_TAB_ACTIVE:
-      *font_weight = gfx::Font::Weight::BOLD;
+      *font_weight = Font::Weight::BOLD;
       break;
-    default:
-      *font_weight = gfx::Font::Weight::NORMAL;
+    case style::STYLE_DIALOG_BUTTON_DEFAULT:
+      // Only non-MD default buttons should "increase" in boldness.
+      if (context == style::CONTEXT_BUTTON) {
+        *font_weight = GetValueBolderThan(
+            ResourceBundle::GetSharedInstance()
+                .GetFontListWithDelta(*size_delta, Font::NORMAL, *font_weight)
+                .GetFontWeight());
+      }
       break;
   }
 }
 
-SkColor DefaultTypographyProvider::GetColor(int context, int style) const {
-  return SK_ColorBLACK;
-}
-
-int DefaultTypographyProvider::GetLineHeight(int context, int style) const {
-  return 0;
-}
-
 }  // namespace views