Add SlidingAverage to FPSMeter, use for WebVR prediction time

device/vr/android/gvr/gvr_delegate.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "device/vr/android/gvr/gvr_delegate.h"
 
 #include "base/trace_event/trace_event.h"
 #include "device/vr/vr_math.h"
 #include "third_party/gvr-android-sdk/src/libraries/headers/vr/gvr/capi/include/gvr.h"
 #include "third_party/gvr-android-sdk/src/libraries/headers/vr/gvr/capi/include/gvr_types.h"
@@ skipping 100 matching lines @@
     pose->position.value()[0] = decomposed_transform.translate[0];
     pose->position.value()[1] = decomposed_transform.translate[1];
     pose->position.value()[2] = decomposed_transform.translate[2];
   }
 
   return pose;
 }
 
 /* static */
 void GvrDelegate::GetGvrPoseWithNeckModel(gvr::GvrApi* gvr_api,
-                                          vr::Mat4f* out) {
+                                          vr::Mat4f* out,
+                                          int64_t prediction_time) {
   gvr::ClockTimePoint target_time = gvr::GvrApi::GetTimePointNow();
-  target_time.monotonic_system_time_nanos += kPredictionTimeWithoutVsyncNanos;
+  target_time.monotonic_system_time_nanos += prediction_time;
 
   gvr::Mat4f head_mat = gvr_api->ApplyNeckModel(
       gvr_api->GetHeadSpaceFromStartSpaceRotation(target_time), 1.0f);
 
   GvrMatToMatf(head_mat, out);
 }
 
 /* static */
+void GvrDelegate::GetGvrPoseWithNeckModel(gvr::GvrApi* gvr_api,
+                                          vr::Mat4f* out) {
+  GetGvrPoseWithNeckModel(gvr_api, out, kPredictionTimeWithoutVsyncNanos);
+}
+
+/* static */
 mojom::VRPosePtr GvrDelegate::GetVRPosePtrWithNeckModel(
     gvr::GvrApi* gvr_api,
-    vr::Mat4f* head_mat_out) {
+    vr::Mat4f* head_mat_out,
+    int64_t prediction_time) {
   gvr::ClockTimePoint target_time = gvr::GvrApi::GetTimePointNow();
-  target_time.monotonic_system_time_nanos += kPredictionTimeWithoutVsyncNanos;
+  target_time.monotonic_system_time_nanos += prediction_time;
 
   gvr::Mat4f gvr_head_mat = gvr_api->ApplyNeckModel(
       gvr_api->GetHeadSpaceFromStartSpaceRotation(target_time), 1.0f);
 
   vr::Mat4f* head_mat_ptr = head_mat_out;
   vr::Mat4f head_mat;
   if (!head_mat_ptr)
     head_mat_ptr = &head_mat;
   GvrMatToMatf(gvr_head_mat, head_mat_ptr);
 
@@ skipping 12 matching lines @@
   gfx::Vector3dF angular_velocity =
       GetAngularVelocityFromPoses(*head_mat_ptr, head_mat_2, epsilon_seconds);
   pose->angularVelocity.value()[0] = angular_velocity.x();
   pose->angularVelocity.value()[1] = angular_velocity.y();
   pose->angularVelocity.value()[2] = angular_velocity.z();
 
   return pose;
 }
 
 /* static */
+mojom::VRPosePtr GvrDelegate::GetVRPosePtrWithNeckModel(
+    gvr::GvrApi* gvr_api,
+    vr::Mat4f* head_mat_out) {
+  return GetVRPosePtrWithNeckModel(gvr_api, head_mat_out,
+                                   kPredictionTimeWithoutVsyncNanos);
+}
+
+/* static */
 gfx::Size GvrDelegate::GetRecommendedWebVrSize(gvr::GvrApi* gvr_api) {
   // Pick a reasonable default size for the WebVR transfer surface
   // based on a downscaled 1:1 render resolution. This size will also
   // be reported to the client via CreateVRDisplayInfo as the
   // client-recommended renderWidth/renderHeight and for the GVR
   // framebuffer. If the client chooses a different size or resizes it
   // while presenting, we'll resize the transfer surface and GVR
   // framebuffer to match.
   gvr::Sizei render_target_size =
       gvr_api->GetMaximumEffectiveRenderTargetSize();
@@ skipping 58 matching lines @@
     gvr::Mat4f eye_mat = gvr_api->GetEyeFromHeadMatrix(eye);
     eye_params->offset[0] = -eye_mat.m[0][3];
     eye_params->offset[1] = -eye_mat.m[1][3];
     eye_params->offset[2] = -eye_mat.m[2][3];
   }
 
   return device;
 }
 
 }  // namespace device