Allow VRDisplay to specify which frame the layer bounds should be updated at.

device/vr/android/gvr/gvr_delegate.h

Index: device/vr/android/gvr/gvr_delegate.h
diff --git a/device/vr/android/gvr/gvr_delegate.h b/device/vr/android/gvr/gvr_delegate.h
index b96e3669533ab69f13d462ec28411deeae8f5f06..57d4d87da707b4c412ca41b0d6975bbc921223e2 100644
--- a/device/vr/android/gvr/gvr_delegate.h
+++ b/device/vr/android/gvr/gvr_delegate.h
@@ -22,7 +22,8 @@ class DEVICE_VR_EXPORT GvrDelegate {
  public:
   virtual void SetWebVRSecureOrigin(bool secure_origin) = 0;
   virtual void SubmitWebVRFrame() = 0;
-  virtual void UpdateWebVRTextureBounds(const gvr::Rectf& left_bounds,
+  virtual void UpdateWebVRTextureBounds(int16_t frame_index,
+                                        const gvr::Rectf& left_bounds,
                                         const gvr::Rectf& right_bounds) = 0;
   virtual gvr::Sizei GetWebVRCompositorSurfaceSize() = 0;
   virtual void SetWebVRRenderSurfaceSize(int width, int height) = 0;