Debugging test failures from https://codereview.chromium.org/291843012/

ui/compositor/layer_animator_collection.cc

Index: ui/compositor/layer_animator_collection.cc
diff --git a/ui/compositor/layer_animator_collection.cc b/ui/compositor/layer_animator_collection.cc
new file mode 100644
index 0000000000000000000000000000000000000000..abdf157d651a22157788ea2b5cf52b4393b3253a
--- /dev/null
+++ b/ui/compositor/layer_animator_collection.cc
@@ -0,0 +1,55 @@
+// Copyright 2014 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 "ui/compositor/layer_animator_collection.h"
+
+#include <set>
+
+#include "base/time/time.h"
+#include "ui/compositor/layer_animator.h"
+#include "ui/gfx/frame_time.h"
+
+namespace ui {
+
+LayerAnimatorCollection::LayerAnimatorCollection(
+    LayerAnimatorCollectionDelegate* delegate)
+    : delegate_(delegate),
+      last_tick_time_(gfx::FrameTime::Now()) {
+}
+
+LayerAnimatorCollection::~LayerAnimatorCollection() {
+}
+
+void LayerAnimatorCollection::StartAnimator(
+    scoped_refptr<LayerAnimator> animator) {
+  if (!animators_.size())
+    last_tick_time_ = gfx::FrameTime::Now();
+  animators_.insert(animator);
+  if (delegate_)
+    delegate_->ScheduleAnimationForLayerCollection();
+}
+
+void LayerAnimatorCollection::StopAnimator(
+    scoped_refptr<LayerAnimator> animator) {
+  DCHECK_GT(animators_.count(animator), 0U);
+  animators_.erase(animator);
+}
+
+bool LayerAnimatorCollection::HasActiveAnimators() const {
+  return !animators_.empty();
+}
+
+void LayerAnimatorCollection::Progress(base::TimeTicks now) {
+  std::set<scoped_refptr<LayerAnimator> > list = animators_;
+  for (std::set<scoped_refptr<LayerAnimator> >::iterator iter = list.begin();
+       iter != list.end();
+       ++iter) {
+    // Make sure the animator is still valid.
+    if (animators_.count(*iter) > 0)
+      (*iter)->Step(now);
+  }
+  last_tick_time_ = now;
+}
+
+}  // namespace ui