Control the VrShell content quad via the HTML UI.

chrome/browser/android/vr_shell/ui_elements.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_ELEMENTS_H_
 #define CHROME_BROWSER_ANDROID_VR_SHELL_UI_ELEMENTS_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 62 matching lines @@
   // If true, this object will be visible.
   bool visible = true;
 
   // If false, the reticle will not hit the element, even if visible.
   bool hit_testable = true;
 
   // If true, transformations will be applied relative to the field of view,
   // rather than the world.
   bool lock_to_fov = false;
 
+  // If true, this element is the content quad. Only one content quad may be
+  // added to the scene.
+  bool content_quad = false;
+
   // Specifies the region (in pixels) of a texture to render.
   Recti copy_rect = {0, 0, 0, 0};
 
   // The size of the object.  This does not affect children.
   gvr::Vec3f size = {1.0f, 1.0f, 1.0f};
 
   // The scale of the object, and its children.
   gvr::Vec3f scale = {1.0f, 1.0f, 1.0f};
 
   // The rotation of the object, and its children.
@@ skipping 12 matching lines @@
   // Animations that affect the properties of the object over time.
   std::vector<std::unique_ptr<Animation>> animations;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ContentRectangle);
 };
 
 }  // namespace vr_shell
 
 #endif  // CHROME_BROWSER_ANDROID_VR_SHELL_UI_ELEMENTS_H_