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

chrome/browser/android/vr_shell/ui_scene.h

 // 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.
 
 #ifndef CHROME_BROWSER_ANDROID_VR_SHELL_UI_SCENE_H_
 #define CHROME_BROWSER_ANDROID_VR_SHELL_UI_SCENE_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 52 matching lines @@
   UiElement* GetUiElementByDebugId(UiElementDebugId debug_id) const;
 
   std::vector<const UiElement*> GetWorldElements() const;
   std::vector<const UiElement*> GetOverlayElements() const;
   std::vector<const UiElement*> GetHeadLockedElements() const;
   bool HasVisibleHeadLockedElements() const;
 
   void SetMode(ColorScheme::Mode mode);
   ColorScheme::Mode mode() const;
 
-  SkColor GetBackgroundColor() const;
+  SkColor GetWorldBackgroundColor() const;
 
   void SetBackgroundDistance(float distance);
   float GetBackgroundDistance() const;
 
   bool GetWebVrRenderingEnabled() const;
   void SetWebVrRenderingEnabled(bool enabled);
 
   bool is_exiting() const { return is_exiting_; }
   void set_is_exiting();
 
@@ skipping 11 matching lines @@
   bool webvr_rendering_enabled_ = true;
   bool gl_initialized_ = false;
   bool is_exiting_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(UiScene);
 };
 
 }  // namespace vr_shell
 
 #endif  // CHROME_BROWSER_ANDROID_VR_SHELL_UI_SCENE_H_