Allow various font weights in gfx.

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 66ffc40bd58241ba2d58b983cc48c1bcb59a2fdd..63a0cbd2bbf05d8aa94ea46e661d77a13df3212e 100644
--- a/ui/gfx/platform_font_mac.h
+++ b/ui/gfx/platform_font_mac.h
@@ -21,8 +21,11 @@ class PlatformFontMac : public PlatformFont {
                   int font_size);
 
   // Overridden from PlatformFont:
-  Font DeriveFont(int size_delta, int style) const override;
+  Font DeriveFont(int size_delta,
+                  int style,
+                  Font::Weight weight) const override;
   int GetHeight() override;
+  Font::Weight GetWeight() const override;
   int GetBaseline() override;
   int GetCapHeight() override;
   int GetExpectedTextWidth(int length) override;
@@ -34,7 +37,10 @@ class PlatformFontMac : public PlatformFont {
   NativeFont GetNativeFont() const override;
 
  private:
-  PlatformFontMac(const std::string& font_name, int font_size, int font_style);
+  PlatformFontMac(const std::string& font_name,
+                  int font_size,
+                  int font_style,
+                  Font::Weight font_weight);
   ~PlatformFontMac() override;
 
   // Calculates and caches the font metrics and inits |render_params_|.
@@ -51,6 +57,7 @@ class PlatformFontMac : public PlatformFont {
   std::string font_name_;  // Corresponds to -[NSFont fontFamily].
   int font_size_;
   int font_style_;
+  Font::Weight font_weight_;
 
   // Cached metrics, generated in CalculateMetrics().
   int height_;