WebVR: add angular velocity estimate to pose

chrome/browser/android/vr_shell/vr_shell.h

Index: chrome/browser/android/vr_shell/vr_shell.h
diff --git a/chrome/browser/android/vr_shell/vr_shell.h b/chrome/browser/android/vr_shell/vr_shell.h
index 7a3de3000f39c4ee92d3cc28a4516f973d1463f3..61579a5e96ff19ee24f944a97c037b1eb6d6e947 100644
--- a/chrome/browser/android/vr_shell/vr_shell.h
+++ b/chrome/browser/android/vr_shell/vr_shell.h
@@ -182,14 +182,36 @@ class VrShell : public device::GvrDelegate,
   void UpdateGamepadData(device::GvrGamepadData) override;
   void RegisterGamepadDataFetcher(device::GvrGamepadDataFetcher*) override;
 
-  // TODO(mthiesse): Find a better place for these functions to live.
-  static device::mojom::VRPosePtr VRPosePtrFromGvrPose(gvr::Mat4f head_mat);
+  // TODO(mthiesse): Find a better place for these functions to live. They are
+  // called from both vr_shell_gl and non_presenting_gvr_delegate.
+
+  // Creates a WebVR pose from a GVR pose, including filling in an angular
+  // velocity estimate based on the change between two predicted poses.
+  static device::mojom::VRPosePtr VRPosePtrFromGvrPose(
+      gvr::Mat4f head_matrix_predicted,
+      gvr::Mat4f head_matrix_for_angular_velocity,
+      int64_t epsilon_nanos);
+
+  // Provides a recommended render resolution for WebVR, this is passed on to
+  // the application as renderWidth/Height
   static gvr::Sizei GetRecommendedWebVrSize(gvr::GvrApi* gvr_api);
+
+  // Fill in the VRDisplayInfo based on recommended size and other headset
+  // parameters.
   static device::mojom::VRDisplayInfoPtr CreateVRDisplayInfo(
       gvr::GvrApi* gvr_api,
       gvr::Sizei recommended_size,
       uint32_t device_id);
 
+  // TODO(mthiesse): If gvr::PlatformInfo().GetPosePredictionTime() is ever
+  // 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 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;
+
  private:
   ~VrShell() override;
   void PostToGlThreadWhenReady(const base::Closure& task);