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

ui/views/style/typography_provider.h

Index: ui/views/style/typography_provider.h
diff --git a/ui/views/style/typography_provider.h b/ui/views/style/typography_provider.h
index aab1c0e997d7a325fd33671e07f3756dcea28cfd..684f751f9c43ba5225a5153d7fc0c8da6e9f5bbf 100644
--- a/ui/views/style/typography_provider.h
+++ b/ui/views/style/typography_provider.h
@@ -31,6 +31,11 @@ class VIEWS_EXPORT TypographyProvider {
   // Gets the line spacing, or 0 if it should be provided by gfx::FontList.
   virtual int GetLineHeight(int context, int style) const = 0;
 
+  // A user's gfx::Weight::NORMAL font may already "bold enough" and requesting
+  // a MEDIUM font can result in a font that is less bold. So this method
+  // returns NORMAL, if the NORMAL font is at least as bold as |weight|.
+  static gfx::Font::Weight WeightNotLighterThanNormal(gfx::Font::Weight weight);
+
  protected:
   TypographyProvider() = default;
 
@@ -52,10 +57,10 @@ class VIEWS_EXPORT DefaultTypographyProvider : public TypographyProvider {
   // Sets the |size_delta| and |font_weight| that the the default GetFont()
   // implementation uses. Always sets values, even for styles it doesn't know
   // about.
-  void GetDefaultFont(int context,
-                      int style,
-                      int* size_delta,
-                      gfx::Font::Weight* font_weight) const;
+  static void GetDefaultFont(int context,
+                             int style,
+                             int* size_delta,
+                             gfx::Font::Weight* font_weight);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DefaultTypographyProvider);