Refactor ActivityStatus to not store current activity

base/android/java/src/org/chromium/base/ActivityState.java

+// 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.
+
+package org.chromium.base;
+
+/**
+ * A set of states that represent the last state change of an Activity.
+ */
+public interface ActivityState {
+    /**
+     * Represents Activity#onCreate().
+     */
+    public final int CREATED = 1;
+
+    /**
+     * Represents Activity#onStart().
+     */
+    public final int STARTED = 2;
+
+    /**
+     * Represents Activity#onResume().
+     */
+    public final int RESUMED = 3;
+
+    /**
+     * Represents Activity#onPause().
+     */
+    public final int PAUSED = 4;
+
+    /**
+     * Represents Activity#onStop().
+     */
+    public final int STOPPED = 5;
+
+    /**
+     * Represents Activity#onDestroy().  This is also used when the state of an Activity is unknown.
+     */
+    public final int DESTROYED = 6;
+}