Add pose age TRACE_COUNTERs for VR/XR gamepads

This helps provide an estimate how old the poses are when polled
by the gamepad API and when read from JavaScript.

BUG=878181

Cq-Include-Trybots: luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I623b876cff559709ff858d9df0ee1df33b736481
Reviewed-on: https://chromium-review.googlesource.com/1200569Reviewed-by: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>
Reviewed-by: Bill Orr <billorr@chromium.org>
Commit-Queue: Klaus Weidner <klausw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590159}

device/gamepad/gamepad_data_fetcher.cc

@@ -33,9 +33,14 @@ void GamepadDataFetcher::ResetVibration(
       mojom::GamepadHapticsResult::GamepadHapticsResultError);
 }
 
+// static
+int64_t GamepadDataFetcher::TimeInMicroseconds(base::TimeTicks update_time) {
+  return update_time.since_origin().InMicroseconds();
+}
+
 // static
 int64_t GamepadDataFetcher::CurrentTimeInMicroseconds() {
-  return base::TimeTicks::Now().since_origin().InMicroseconds();
+  return TimeInMicroseconds(base::TimeTicks::Now());
 }
 
 GamepadDataFetcherFactory::GamepadDataFetcherFactory() = default;

device/gamepad/gamepad_data_fetcher.h

@@ -44,6 +44,10 @@ class DEVICE_GAMEPAD_EXPORT GamepadDataFetcher {
   // the value returned by this method to update the |timestamp| gamepad member.
   static int64_t CurrentTimeInMicroseconds();
 
+  // Converts a TimeTicks value to a timestamp in microseconds, as used for
+  // the |timestamp| gamepad member.
+  static int64_t TimeInMicroseconds(base::TimeTicks update_time);
+
  protected:
   friend GamepadPadStateProvider;
 

device/vr/isolated_gamepad_data_fetcher.cc

@@ -139,7 +139,7 @@ void IsolatedGamepadDataFetcher::GetGamepadData(bool devices_changed_hint) {
     dest.connected = true;
 
     seen_gamepads.insert(source->controller_id);
-    dest.timestamp = CurrentTimeInMicroseconds();
+    dest.timestamp = TimeInMicroseconds(source->timestamp);
     dest.pose = GamepadPoseFromXRPose(source->pose.get());
     dest.pose.has_position = source->can_provide_position;
     dest.pose.has_orientation = source->can_provide_orientation;
@@ -181,6 +181,10 @@ void IsolatedGamepadDataFetcher::GetGamepadData(bool devices_changed_hint) {
       }
     }
 
+    TRACE_COUNTER1(
+        "input", "XR gamepad sample age (ms)",
+        (base::TimeTicks::Now() - source->timestamp).InMilliseconds());
+
     dest.mapping[0] = 0;
   }
 

device/vr/oculus/oculus_gamepad_helper.cc

@@ -163,6 +163,7 @@ void AddTouchData(mojom::XRGamepadDataPtr& data,
   gamepad->pose = std::move(dst_pose);
   gamepad->can_provide_position = true;
   gamepad->can_provide_orientation = true;
+  gamepad->timestamp = base::TimeTicks::Now();
   data->gamepads.push_back(std::move(gamepad));
 }
 

device/vr/openvr/openvr_gamepad_helper.cc

@@ -60,6 +60,8 @@ mojom::XRGamepadDataPtr OpenVRGamepadHelper::GetGamepadData(
     auto gamepad = mojom::XRGamepad::New();
     gamepad->controller_id = i;
 
+    gamepad->timestamp = base::TimeTicks::Now();
+
     vr::ETrackedControllerRole hand =
         vr_system->GetControllerRoleForTrackedDeviceIndex(i);
     switch (hand) {

device/vr/public/mojom/isolated_xr_service.mojom

@@ -5,6 +5,7 @@
 module device.mojom;
 
 import "device/vr/public/mojom/vr_service.mojom";
+import "mojo/public/mojom/base/time.mojom";
 
 const string kVrIsolatedServiceName = "xr_device_service";
 
@@ -100,6 +101,9 @@ struct XRGamepad {
   // A unique (per device_id) id that allows controllers to be tracked between
   // updates.  Useful to identify controllers as they are added/removed.
   uint32 controller_id;
+
+  // The time at which this pose was retrieved.
+  mojo_base.mojom.TimeTicks timestamp;
 };
 
 // Represents the state of a set of controllers driven by some runtime API.

third_party/blink/renderer/modules/gamepad/navigator_gamepad.cc

@@ -108,6 +108,12 @@ static void SampleGamepad(size_t index,
   gamepad.SetPose(device_gamepad.pose);
   gamepad.SetHand(device_gamepad.hand);
 
+  if (device_gamepad.is_xr) {
+    TimeTicks now = TimeTicks::Now();
+    TRACE_COUNTER1("input", "XR gamepad pose age (ms)",
+                   (now - last_updated).InMilliseconds());
+  }
+
   bool newly_connected;
   HasGamepadConnectionChanged(old_id, gamepad.id(), old_was_connected,
                               gamepad.connected(), &newly_connected, nullptr);