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 8222cf673571d9773ab5ceed7ff6a98b0f5e028e..e9b86d4129c6347733ae4e87981c11672e988624 100644
--- a/device/vr/android/gvr/gvr_delegate.h
+++ b/device/vr/android/gvr/gvr_delegate.h
@@ -21,7 +21,8 @@ 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;