Add NetworkChangeNotifier for Android.

base/android/java/org/chromium/base/ActivityStatus.java

Index: base/android/java/org/chromium/base/ActivityStatus.java
diff --git a/base/android/java/org/chromium/base/ActivityStatus.java b/base/android/java/org/chromium/base/ActivityStatus.java
new file mode 100644
index 0000000000000000000000000000000000000000..765d8411d4b4337a952d70929a2696d776c412ba
--- /dev/null
+++ b/base/android/java/org/chromium/base/ActivityStatus.java
@@ -0,0 +1,83 @@
+// Copyright (c) 2012 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;
+
+import android.os.Looper;
+
+import java.util.ArrayList;
+
+/**
+ * Provides information about the parent activity's status.
+ */
+public class ActivityStatus {
+    public interface Listener {
+        /**
+         * Called when the activity's status changes.
+         * @param isPaused true if the activity is paused, false if not.
+         */
+        public void onActivityStatusChanged(boolean isPaused);
+    }
+
+    private boolean mIsPaused = false;
+    private ArrayList<Listener> mListeners = new ArrayList<Listener>();
+    private static ActivityStatus sActivityStatus;
+
+    private ActivityStatus() {
+    }
+
+    public static ActivityStatus getInstance() {
+        // Can only be called on the UI thread.
+        assert Looper.myLooper() == Looper.getMainLooper();
+        if (sActivityStatus == null) {
+            sActivityStatus = new ActivityStatus();
+        }
+        return sActivityStatus;
+    }
+
+    /**
+     * Indicates that the parent activity was paused.
+     */
+    public void onPause() {
+        mIsPaused = true;
+        informAllListeners();
+    }
+
+    /**
+     * Indicates that the parent activity was resumed.
+     */
+    public void onResume() {
+        mIsPaused = false;
+        informAllListeners();
+    }
+
+    /**
+     * Indicates that the parent activity is currently paused.
+     */
+    public boolean isPaused() {
+        return mIsPaused;
+    }
+
+    /**
+     * Registers the given listener to receive activity status updates.
+     * @param listener Listener to receive status updates.
+     */
+    public void registerListener(Listener listener) {
+        mListeners.add(listener);
+    }
+
+    /**
+     * Unregisters the given listener from receiving activity status updates.
+     * @param listener Listener that doesn't want to receive status updates.
+     */
+    public void unregisterListener(Listener listener) {
+        mListeners.remove(listener);
+    }
+
+    private void informAllListeners() {
+        for (Listener listener : mListeners) {
+            listener.onActivityStatusChanged(mIsPaused);
+        }
+    }
+}