VrShell: Allow native control of UI element opacity.

chrome/browser/android/vr_shell/vr_shell_renderer.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_VR_SHELL_RENDERER_H_
 #define CHROME_BROWSER_ANDROID_VR_SHELL_VR_SHELL_RENDERER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 35 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(BaseRenderer);
 };
 
 class TexturedQuadRenderer : public BaseRenderer {
  public:
   TexturedQuadRenderer();
   ~TexturedQuadRenderer() override;
 
   // Draw the content rect in the texture quad.
   void Draw(int texture_data_handle, const gvr::Mat4f& combined_matrix,
-            const Rectf& copy_rect);
+            const Rectf& copy_rect, float opacity);
 
  private:
   GLuint combined_matrix_handle_;
   GLuint copy_rect_uniform_handle_;
   GLuint tex_uniform_handle_;
+  GLuint opacity_handle_;
 
   DISALLOW_COPY_AND_ASSIGN(TexturedQuadRenderer);
 };
 
 // Renders a page-generated stereo VR view.
 class WebVrRenderer : public BaseRenderer {
  public:
   WebVrRenderer();
   ~WebVrRenderer() override;
 
@@ skipping 74 matching lines @@
   std::unique_ptr<WebVrRenderer> webvr_renderer_;
   std::unique_ptr<ReticleRenderer> reticle_renderer_;
   std::unique_ptr<LaserRenderer> laser_renderer_;
 
   DISALLOW_COPY_AND_ASSIGN(VrShellRenderer);
 };
 
 }  // namespace vr_shell
 
 #endif  // CHROME_BROWSER_ANDROID_VR_SHELL_VR_SHELL_RENDERER_H_