Define accelerated steps time function.

ui/gfx/animation/steps.cc

Index: ui/gfx/animation/steps.cc
diff --git a/ui/gfx/animation/steps.cc b/ui/gfx/animation/steps.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0fe6a47cd9e29c3da48d8d98b4ce653ad60192e0
--- /dev/null
+++ b/ui/gfx/animation/steps.cc
@@ -0,0 +1,39 @@
+// 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/gfx/animation/steps.h"
+
+#include <cmath>
+
+#include "base/logging.h"
+
+template <class T>
+T clamp(T value, T min, T max) {
+  if (value < min)
+    value = min;
+  if (value > max)
+    value = max;
+  return value;
+}
+
+namespace gfx {
+
+Steps::Steps(int steps, bool steps_at_start)
+    : steps_(steps), steps_at_start_(steps_at_start) {
+}
+
+Steps::~Steps() {
+}
+
+double Steps::Solve(double x) const {
+  x = clamp(x, 0.0, 1.0);
+  return std::min(1.0, (floor(steps_ * x) + steps_at_start_) / steps_);
+}
+
+void Steps::Range(double* min, double* max) const {
+  *min = static_cast<double>(steps_at_start_) / static_cast<double>(steps_);
+  *max = 1.0;
+}
+
+}  // namespace gfx