[VrShell] Centralize color handling and enable close button on fullscreen

chrome/browser/android/vr_shell/color_scheme.h

Index: chrome/browser/android/vr_shell/color_scheme.h
diff --git a/chrome/browser/android/vr_shell/color_scheme.h b/chrome/browser/android/vr_shell/color_scheme.h
index 9f14c5ac2959919a06a9eeba054759a00f44bc31..b8a507ddb0b652438e120b4ee35375aa48facd95 100644
--- a/chrome/browser/android/vr_shell/color_scheme.h
+++ b/chrome/browser/android/vr_shell/color_scheme.h
@@ -21,21 +21,22 @@ struct ColorScheme {
 
   // These colors should be named generically, if possible, so that they can be
   // meaningfully reused by multiple elements.
-  SkColor horizon;
+  SkColor world_background;

[cjgrant, 2017/05/31 15:39:28]

This more verbose naming looks great to me.

[amp, 2017/06/02 01:08:35]

Acknowledged.

   SkColor floor;
   SkColor ceiling;
   SkColor floor_grid;
 
   // The foreground color is used for text and sometimes for icons.
-  SkColor foreground;
-  SkColor emphasized;
-  SkColor deemphasized;
-
-  // This is the background color. To be used behind text in the foreground
-  // color. The related hover and down colors are to be used for buttons.
-  SkColor background;
-  SkColor background_hover;
-  SkColor background_down;
+  SkColor element_foreground;
+  SkColor text_emphasized;
+  SkColor text_deemphasized;
+
+  // This is the element background color. To be used behind text or icons in
+  // the foreground color. The related hover and down colors are to be used for
+  // buttons.
+  SkColor element_background;
+  SkColor element_background_hover;
+  SkColor element_background_down;
 
   // If you have a segmented element, its separators should use this color.
   SkColor separator;