[Android] Add progress bar linear animation option.

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

+// Copyright 2015 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;
+
+/**
+ * Progress bar animation logic that has linear speed.
+ */
+class ProgressAnimationLinear implements ToolbarProgressBar.AnimationLogic {
+    // The speed unit is progress per second where 0 <= progress <= 1.
+    private static final float NORMAL_SPEED = 0.5f;
+    private static final float FINISHING_SPEED = 2.0f;
+
+    private float mProgress;
+
+    @Override
+    public void reset() {
+        mProgress = 0.0f;
+    }
+
+    @Override
+    public float updateProgress(float targetProgress, float frameTimeSec, int resolution) {
+        assert mProgress <= targetProgress;
+
+        mProgress = Math.min(targetProgress, mProgress
+                + frameTimeSec * (targetProgress == 1.0f ? FINISHING_SPEED : NORMAL_SPEED));
+        return mProgress;
+    }
+}