[CRD iOS] Viewport fling animation

remoting/client/fling_animation.cc

Index: remoting/client/fling_animation.cc
diff --git a/remoting/client/fling_animation.cc b/remoting/client/fling_animation.cc
new file mode 100644
index 0000000000000000000000000000000000000000..109a5c4e3d0d85dce4c4f0c37f26c7cbd522c1f0
--- /dev/null
+++ b/remoting/client/fling_animation.cc
@@ -0,0 +1,46 @@
+// Copyright 2017 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 "remoting/client/fling_animation.h"
+
+#include "base/time/default_tick_clock.h"
+
+namespace remoting {
+
+FlingAnimation::FlingAnimation(float time_constant,
+                               const FlingCallback& fling_callback)
+    : fling_tracker_(time_constant),
+      fling_callback_(fling_callback),
+      clock_(new base::DefaultTickClock()) {}
+
+FlingAnimation::~FlingAnimation() {}
+
+void FlingAnimation::SetVelocity(float velocity_x, float velocity_y) {
+  fling_tracker_.StartFling(velocity_x, velocity_y);
+  fling_start_time_ = clock_->NowTicks();
+}
+
+bool FlingAnimation::IsAnimationInProgress() const {
+  return fling_tracker_.IsFlingInProgress();
+}
+
+void FlingAnimation::Tick() {
+  float dx, dy;
+  bool in_progress = fling_tracker_.TrackMovement(
+      clock_->NowTicks() - fling_start_time_, &dx, &dy);

[nicholss, 2017/05/11 15:13:50]

I think this looks much cleaner, I hope you agree. 

[Yuwei, 2017/05/11 18:26:27]

Yep, and it's also for testability.

+  if (in_progress) {
+    fling_callback_.Run(dx, dy);
+  }
+}
+
+void FlingAnimation::Abort() {
+  fling_tracker_.StopFling();
+}
+
+void FlingAnimation::SetTickClockForTest(
+    std::unique_ptr<base::TickClock> clock) {
+  clock_ = std::move(clock);
+}
+
+}  // namespace remoting