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

chrome/browser/android/vr_shell/non_presenting_gvr_delegate.cc

Index: chrome/browser/android/vr_shell/non_presenting_gvr_delegate.cc
diff --git a/chrome/browser/android/vr_shell/non_presenting_gvr_delegate.cc b/chrome/browser/android/vr_shell/non_presenting_gvr_delegate.cc
index da7ec3f758e15f23ccd8dc0623cfdce7113a2ffe..36ab13acb57253da269cf466b5fcdf9505c29f2c 100644
--- a/chrome/browser/android/vr_shell/non_presenting_gvr_delegate.cc
+++ b/chrome/browser/android/vr_shell/non_presenting_gvr_delegate.cc
@@ -56,8 +56,10 @@ NonPresentingGvrDelegate::OnSwitchToPresentingDelegate() {
 
 void NonPresentingGvrDelegate::StopVSyncLoop() {
   vsync_task_.Cancel();
-  if (!callback_.is_null())
-    callback_.Run(nullptr, base::TimeDelta());
+  if (!callback_.is_null()) {
+    callback_.Run(nullptr, base::TimeDelta(), -1);

[dcheng, 2017/01/27 09:41:33]

One possibility (if you want) is base::ResetAndReturn(...).Run(...);

[mthiesse, 2017/01/27 16:15:31]

That works well, thanks!

+    callback_.Reset();
+  }
   callback_.Reset();
   gvr_api_->PauseTracking();
   // If the loop is stopped, it's not considered to be paused.
@@ -94,7 +96,7 @@ void NonPresentingGvrDelegate::OnVSync() {
 
   base::TimeDelta time = intervals * vsync_interval_;
   if (!callback_.is_null()) {
-    callback_.Run(GetPose(), time);
+    SendVSync(time, callback_);
     callback_.Reset();
   } else {
     pending_vsync_ = true;
@@ -113,7 +115,7 @@ void NonPresentingGvrDelegate::GetVSync(const GetVSyncCallback& callback) {
     return;
   }
   pending_vsync_ = false;
-  callback.Run(GetPose(), pending_time_);
+  SendVSync(pending_time_, callback);
 }
 
 void NonPresentingGvrDelegate::UpdateVSyncInterval(long timebase_nanos,
@@ -124,17 +126,14 @@ void NonPresentingGvrDelegate::UpdateVSyncInterval(long timebase_nanos,
   StartVSyncLoop();
 }
 
-device::mojom::VRPosePtr NonPresentingGvrDelegate::GetPose() {
+void NonPresentingGvrDelegate::SendVSync(base::TimeDelta time,
+                                         const GetVSyncCallback& callback) {
   gvr::ClockTimePoint target_time = gvr::GvrApi::GetTimePointNow();
   target_time.monotonic_system_time_nanos += kPredictionTimeWithoutVsyncNanos;
 
-  gvr::Mat4f head_mat =
-      gvr_api_->GetHeadSpaceFromStartSpaceRotation(target_time);
-  head_mat = gvr_api_->ApplyNeckModel(head_mat, 1.0f);
-
-  uint32_t pose_index = pose_index_++;
-
-  return VrShell::VRPosePtrFromGvrPose(head_mat, pose_index);
+  gvr::Mat4f head_mat = gvr_api_->ApplyNeckModel(
+      gvr_api_->GetHeadSpaceFromStartSpaceRotation(target_time), 1.0f);
+  callback.Run(VrShell::VRPosePtrFromGvrPose(head_mat), time, -1);
 }
 
 }  // namespace vr_shell