ash: Add basic prediction code to the laser pointer.

ash/laser/laser_pointer_points.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 "ash/laser/laser_pointer_points.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "ui/gfx/geometry/rect_conversions.h"
 
 namespace ash {
 
 LaserPointerPoints::LaserPointerPoints(base::TimeDelta life_duration)
     : life_duration_(life_duration) {}
 
 LaserPointerPoints::~LaserPointerPoints() {}
 
-void LaserPointerPoints::AddPoint(const gfx::PointF& point) {
-  MoveForwardToTime(base::Time::Now());
+void LaserPointerPoints::AddPoint(const gfx::PointF& point,
+                                  const base::TimeTicks& time) {
+  // Move forward in time if needed.
+  if (time > collection_latest_time_)
+    MoveForwardToTime(time);
 
   LaserPoint new_point;
   new_point.location = point;
+  new_point.time = time;
+  new_point.age = std::min((collection_latest_time_ - time).InMillisecondsF() /
+                               life_duration_.InMillisecondsF(),
+                           1.0);
   points_.push_back(new_point);
 }
 
-void LaserPointerPoints::MoveForwardToTime(const base::Time& latest_time) {
+void LaserPointerPoints::MoveForwardToTime(const base::TimeTicks& latest_time) {
+  DCHECK_GE(latest_time, collection_latest_time_);
+
   if (!points_.empty()) {
     DCHECK(!collection_latest_time_.is_null());
 
     // Increase the age of points based on how much time has elapsed.
     base::TimeDelta delta = latest_time - collection_latest_time_;
     double lifespan_change =
         delta.InMillisecondsF() / life_duration_.InMillisecondsF();
     for (LaserPoint& point : points_)
       point.age += lifespan_change;
 
@@ skipping 35 matching lines @@
 
 bool LaserPointerPoints::IsEmpty() const {
   return points_.empty();
 }
 
 int LaserPointerPoints::GetNumberOfPoints() const {
   return points_.size();
 }
 
 const std::deque<LaserPointerPoints::LaserPoint>&
-LaserPointerPoints::laser_points() {
+LaserPointerPoints::laser_points() const {
   return points_;
 }
 }  // namespace ash