Clean up NativeTheme (particularly CommonTheme).

ui/views/style/platform_style_mac.mm

Index: ui/views/style/platform_style_mac.mm
diff --git a/ui/views/style/platform_style_mac.mm b/ui/views/style/platform_style_mac.mm
index 707c2d9f1f31d36e61122853ea1419bec6853914..866bba64424ff4c8a7f9876c0567c8dbd7287280 100644
--- a/ui/views/style/platform_style_mac.mm
+++ b/ui/views/style/platform_style_mac.mm
@@ -80,10 +80,8 @@ SkColor PlatformStyle::TextColorForButton(
 void PlatformStyle::ApplyLabelButtonTextStyle(

[Evan Stade, 2016/09/30 18:02:36]

this won't be necessary any more when harmony is default (there will be no
STYLE_BUTTON labelbuttons any more)

[tdanderson, 2016/09/30 21:00:56]

Is this something that will be obvious / you will remember when Harmony is
default, or should you add a TODO?

[Evan Stade, 2016/09/30 22:19:00]

should be obvious in the sense that it won't be called from anywhere any more. I
have a TODO in the relevant part of LabelButton.

     views::Label* label,
     ButtonColorByState* color_by_state) {
-  const ui::NativeTheme* theme = label->GetNativeTheme();
   ButtonColorByState& colors = *color_by_state;
-  colors[Button::STATE_PRESSED] =
-      theme->GetSystemColor(ui::NativeTheme::kColorId_ButtonHighlightColor);
+  colors[Button::STATE_PRESSED] = SK_ColorWHITE;
 }
 
 // static