WebVR: add angular velocity estimate to pose

chrome/browser/android/vr_shell/vr_shell_gl.cc

Index: chrome/browser/android/vr_shell/vr_shell_gl.cc
diff --git a/chrome/browser/android/vr_shell/vr_shell_gl.cc b/chrome/browser/android/vr_shell/vr_shell_gl.cc
index 587c233fa5b55a6d3916c2c89d31676ba5df54af..61557cac8118894f5325a8b3a50664c54033eba8 100644
--- a/chrome/browser/android/vr_shell/vr_shell_gl.cc
+++ b/chrome/browser/android/vr_shell/vr_shell_gl.cc
@@ -39,6 +39,11 @@ namespace {
 // exposed, use that instead (it defaults to 50ms on most platforms).
 static constexpr int64_t kPredictionTimeWithoutVsyncNanos = 50000000;
 
+// Time offset used for calculating angular velocity from a pair

[cjgrant, 2017/03/24 21:15:40]

nit: Most editors can be used to auto-format comment blocks.  A few of the
comments don't wrap properly.  "git cl format" might also do it.

[klausw, 2017/03/24 22:13:29]

I was using auto format, but Emacs for some reason defaults to 70 columns.
Fixed.

+// of predicted poses. The precise value shouldn't matter as long as
+// it's nonzero and much less than a frame.
+static constexpr int64_t kAngularVelocityEpsilonNanos = 1000000;
+
 static constexpr float kZNear = 0.1f;
 static constexpr float kZFar = 1000.0f;
 
@@ -1270,9 +1275,15 @@ void VrShellGl::SendVSync(base::TimeDelta time,
       gvr_api_->GetHeadSpaceFromStartSpaceRotation(target_time);
   head_mat = gvr_api_->ApplyNeckModel(head_mat, 1.0f);
 
+  target_time.monotonic_system_time_nanos += kAngularVelocityEpsilonNanos;
+  gvr::Mat4f head_mat_2 =
+      gvr_api_->GetHeadSpaceFromStartSpaceRotation(target_time);
+
   webvr_head_pose_[frame_index % kPoseRingBufferSize] = head_mat;
 
-  callback.Run(VrShell::VRPosePtrFromGvrPose(head_mat), time, frame_index,
+  callback.Run(VrShell::VRPosePtrFromGvrPose(head_mat, head_mat_2,
+                                             kAngularVelocityEpsilonNanos),
+               time, frame_index,
                device::mojom::VRVSyncProvider::Status::SUCCESS);
 }