Gtk3: Rename Gtk2UI and Get[FB]GColor

This is a simple renaming CL.  A global search/replace was done with
the following strings:

Gtk2UI -> GtkUi
GetFGColor -> GetFgColor
GetBGColor -> GetBgColor

BUG=132847

Review-Url: https://codereview.chromium.org/2610883004
Cr-Commit-Position: refs/heads/master@{#441559}
diff --git a/chrome/browser/themes/theme_service.cc b/chrome/browser/themes/theme_service.cc
index 1dad1aa5..9f5b82a 100644
--- a/chrome/browser/themes/theme_service.cc
+++ b/chrome/browser/themes/theme_service.cc
@@ -434,7 +434,7 @@
           gfx::kChromeIconGrey,
           GetTint(ThemeProperties::TINT_BUTTONS, incognito));
     case ThemeProperties::COLOR_TOOLBAR_BUTTON_ICON_INACTIVE:
-      // The active color is overridden in Gtk2UI.
+      // The active color is overridden in GtkUi.
       return SkColorSetA(
           GetColor(ThemeProperties::COLOR_TOOLBAR_BUTTON_ICON, incognito),
           0x33);