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

chrome/browser/android/vr_shell/ui_scene.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/android/vr_shell/ui_scene.h"
 
 #include <string>
 #include <utility>
 
 #include "base/memory/ptr_util.h"
@@ skipping 170 matching lines @@
 
   mode_ = mode;
   for (const auto& element : ui_elements_)
     element->SetMode(mode);
 }
 
 ColorScheme::Mode UiScene::mode() const {
   return mode_;
 }
 
-SkColor UiScene::GetBackgroundColor() const {
-  return ColorScheme::GetColorScheme(mode_).horizon;
+SkColor UiScene::GetWorldBackgroundColor() const {
+  return ColorScheme::GetColorScheme(mode_).world_background;
 }
 
 void UiScene::SetBackgroundDistance(float distance) {
   background_distance_ = distance;
 }
 
 float UiScene::GetBackgroundDistance() const {
   return background_distance_;
 }
 
@@ skipping 59 matching lines @@
 
 // TODO(mthiesse): Move this to UiSceneManager.
 void UiScene::OnGLInitialized() {
   gl_initialized_ = true;
   for (auto& element : ui_elements_) {
     element->Initialize();
   }
 }
 
 }  // namespace vr_shell