VrShell: Allow native control of UI element opacity.

chrome/browser/android/vr_shell/vr_shell_renderer.h

Index: chrome/browser/android/vr_shell/vr_shell_renderer.h
diff --git a/chrome/browser/android/vr_shell/vr_shell_renderer.h b/chrome/browser/android/vr_shell/vr_shell_renderer.h
index b5d7f99561f1e9022c42e3006801a22511d40546..ae4a6a032031a2005d5c130747698c962f004988 100644
--- a/chrome/browser/android/vr_shell/vr_shell_renderer.h
+++ b/chrome/browser/android/vr_shell/vr_shell_renderer.h
@@ -53,12 +53,13 @@ class TexturedQuadRenderer : public BaseRenderer {
 
   // 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);
 };