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

chrome/browser/android/vr_shell/vr_shell_gl.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/vr_shell_gl.h"
 
 #include <chrono>
 #include <limits>
 #include <utility>
 
@@ skipping 1113 matching lines @@
     // existing content in place in the primary buffer without
     // clearing. Currently, there aren't any world elements in WebVR
     // mode, this will need further testing if those get added
     // later.
   } else {
     // Non-WebVR mode, enable depth testing and clear the primary buffers.
     glEnable(GL_CULL_FACE);
     glEnable(GL_DEPTH_TEST);
     glDepthMask(GL_TRUE);
 
-    const SkColor backgroundColor = scene_->GetBackgroundColor();
+    const SkColor backgroundColor = scene_->GetWorldBackgroundColor();
     glClearColor(SkColorGetR(backgroundColor) / 255.0,
                  SkColorGetG(backgroundColor) / 255.0,
                  SkColorGetB(backgroundColor) / 255.0,
                  SkColorGetA(backgroundColor) / 255.0);
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   }
   std::vector<const UiElement*> elements = scene_->GetWorldElements();
   const bool draw_reticle = !(scene_->is_exiting() || ShouldDrawWebVr());
   DrawUiView(head_pose, elements, render_size_primary_,
              kViewportListPrimaryOffset, draw_reticle);
@@ skipping 453 matching lines @@
   // This assumes that the initial webvr_surface_size_ was set to the
   // appropriate recommended render resolution as the default size during
   // InitializeGl. Revisit if the initialization order changes.
   device::mojom::VRDisplayInfoPtr info =
       device::GvrDelegate::CreateVRDisplayInfo(gvr_api_.get(),
                                                webvr_surface_size_, device_id);
   browser_->RunVRDisplayInfoCallback(callback, &info);
 }
 
 }  // namespace vr_shell