Add support for highlighting menu items

chrome/android/java/src/org/chromium/chrome/browser/widget/PulseInterpolator.java

+// 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.
+
+package org.chromium.chrome.browser.widget;
+
+import android.view.animation.Interpolator;
+
+/**
+ * An {@link Interpolator} that pulses a value based on the passed in {@link Interpolator}.  The
+ * pulse will fade in and out after a delay.
+ */
+public class PulseInterpolator implements Interpolator {
+    private final Interpolator mInterpolator;
+
+    /**
+     * Creates a new {@link PulseInterpolator} instance.
+     * @param interpolator The {@link Interpolator} responsible for handling the fade out and in.
+     */
+    public PulseInterpolator(Interpolator interpolator) {
+        mInterpolator = interpolator;
+    }
+
+    @Override
+    public float getInterpolation(float input) {
+        if (input < 0.4f) return 0.f;
+        if (input < 0.8f) return mInterpolator.getInterpolation((input - 0.4f) / 0.4f);
+        return mInterpolator.getInterpolation(1.f - (input - 0.8f) / 0.2f);
+    }
+}