[vr] Add a frame rate counter for the vr UI

chrome/browser/android/vr_shell/vr_shell_gl.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 "chrome/browser/android/vr_shell/vr_shell_gl.h"
 
 #include <chrono>
 #include <limits>
 #include <utility>
 
 #include "base/android/jni_android.h"
 #include "base/callback_helpers.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/threading/thread_task_runner_handle.h"
+#include "cc/trees/frame_rate_counter.h"
 #include "chrome/browser/android/vr_shell/mailbox_to_surface_bridge.h"
 #include "chrome/browser/android/vr_shell/ui_elements.h"
 #include "chrome/browser/android/vr_shell/ui_interface.h"
 #include "chrome/browser/android/vr_shell/ui_scene.h"
 #include "chrome/browser/android/vr_shell/vr_controller.h"
 #include "chrome/browser/android/vr_shell/vr_gl_util.h"
 #include "chrome/browser/android/vr_shell/vr_math.h"
 #include "chrome/browser/android/vr_shell/vr_shell.h"
 #include "chrome/browser/android/vr_shell/vr_shell_renderer.h"
 #include "device/vr/android/gvr/gvr_delegate.h"
@@ skipping 51 matching lines @@
 static constexpr int kViewportListHeadlockedOffset = 2;
 
 // Buffer size large enough to handle the current backlog of poses which is
 // 2-3 frames.
 static constexpr unsigned kPoseRingBufferSize = 8;
 
 // Criteria for considering holding the app button in combination with
 // controller movement as a gesture.
 static constexpr float kMinAppButtonGestureAngleRad = 0.25;
 
+// UI has no "impl" (i.e., separate compositor) thread.
+static constexpr bool kHasImplThread = false;
+
 // Generate a quaternion representing the rotation from the negative Z axis
 // (0, 0, -1) to a specified vector. This is an optimized version of a more
 // general vector-to-vector calculation.
 gvr::Quatf GetRotationFromZAxis(gvr::Vec3f vec) {
   vr_shell::NormalizeVector(vec);
   gvr::Quatf quat;
   quat.qw = 1.0f - vec.z;
   if (quat.qw < 1e-6f) {
     // Degenerate case: vectors are exactly opposite. Replace by an
     // arbitrary 180 degree rotation to avoid invalid normalization.
@@ skipping 43 matching lines @@
     scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner,
     gvr_context* gvr_api,
     bool initially_web_vr,
     bool reprojected_rendering)
     : web_vr_mode_(initially_web_vr),
       surfaceless_rendering_(reprojected_rendering),
       task_runner_(base::ThreadTaskRunnerHandle::Get()),
       binding_(this),
       weak_vr_shell_(weak_vr_shell),
       main_thread_task_runner_(std::move(main_thread_task_runner)),
+      frame_rate_counter_(cc::FrameRateCounter::Create(kHasImplThread)),
       weak_ptr_factory_(this) {
   GvrInit(gvr_api);
 }
 
 VrShellGl::~VrShellGl() {
   vsync_task_.Cancel();
   // TODO(mthiesse): Can we omit the Close() here? Concern is that if
   // both ends of the connection ever live in the same process for
   // some reason, we could receive another VSync request in response
   // to the closing message in the destructor but fail to respond to
@@ skipping 669 matching lines @@
     TRACE_EVENT0("gpu", "VrShellGl::Submit");
     frame.Submit(*buffer_viewport_list_, head_pose);
   }
 
   // No need to swap buffers for surfaceless rendering.
   if (!surfaceless_rendering_) {
     // TODO(mthiesse): Support asynchronous SwapBuffers.
     TRACE_EVENT0("gpu", "VrShellGl::SwapBuffers");
     surface_->SwapBuffers();
   }
+
+  // This is an unused parameter when we do not have a compositor thread.
+  bool unused_is_a_software_compositor = false;
+
+  // After saving the timestamp, a reliable framerate should be available via
+  // GetAverageFPS().
+  // TODO(vollick): enable rendering of this framerate in a HUD.
+  frame_rate_counter_->SaveTimeStamp(current_time,

[mthiesse, 2017/04/07 15:36:33]

I know this is fairly lightweight, but we should probably only be generating
this data when using it, so putting it behind a debug flag for now might be
reasonable?

+                                     unused_is_a_software_compositor);

[mthiesse, 2017/04/07 15:36:33]

nit: Definitely personal preference, but I think this is overly verbose.
I would have written 
frame_rate_counter_->SaveTimeStamp(current_time, false /* unused */);
but feel free to ignore this.

 }
 
 void VrShellGl::DrawWorldElements(const gvr::Mat4f& head_pose) {
   TRACE_EVENT0("gpu", "VrShellGl::DrawWorldElements");
 
   if (ShouldDrawWebVr()) {
     // WebVR is incompatible with 3D world compositing since the
     // depth buffer was already populated with unknown scaling - the
     // WebVR app has full control over zNear/zFar. Just leave the
     // existing content in place in the primary buffer without
@@ skipping 427 matching lines @@
   // InitializeGl. Revisit if the initialization order changes.
   device::mojom::VRDisplayInfoPtr info =
       device::GvrDelegate::CreateVRDisplayInfo(gvr_api_.get(),
                                                webvr_surface_size_, device_id);
   main_thread_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&RunVRDisplayInfoCallback, callback, base::Passed(&info)));
 }
 
 }  // namespace vr_shell