Add a new GetSystemColor method to native theme.

ui/gfx/native_theme_base.cc

Index: ui/gfx/native_theme_base.cc
diff --git a/ui/gfx/native_theme_base.cc b/ui/gfx/native_theme_base.cc
index 95ba5aa1e681b1856e4f246b1c6837bab2157c68..1c47f602a5d22a550c5396ab1632887901cee526 100644
--- a/ui/gfx/native_theme_base.cc
+++ b/ui/gfx/native_theme_base.cc
@@ -57,6 +57,19 @@ NativeThemeBase::NativeThemeBase() {
 NativeThemeBase::~NativeThemeBase() {
 }
 
+// This implementation returns hardcoded colors. It's used by NativeThemeAura
+// and NativeThemeChromeos and overridden by NativeThemeGtk.
+SkColor NativeThemeBase::GetSystemColor(ColorId color_id) const {
+  switch (color_id) {
+    case kDialogBackgroundColor:
+      return SkColorSetRGB(200, 200, 200);

[James Cook, 2011/11/18 23:22:50]

We typically define colors like this as constants in an anonymous namespace,
like:

namespace {

const SkColor kDialogBackgroundColor = ...;

}

even if they are used only once.  That also might imply that the enum should be
named kDialogBackground or kDialogBackgroundColorId or some such.

[benrg, 2011/11/19 00:20:22]

Done.

+    default:
+      NOTREACHED() << "Invalid color_id: " << color_id;
+      break;
+  }
+  return SkColorSetRGB(255, 0, 0);  // warning red
+}
+
 gfx::Size NativeThemeBase::GetPartSize(Part part,
                                        State state,
                                        const ExtraParams& extra) const {