Refactor ActivityStatus to not store current activity

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

Index: base/android/java/src/org/chromium/base/BaseChromiumApplication.java
diff --git a/base/android/java/src/org/chromium/base/BaseChromiumApplication.java b/base/android/java/src/org/chromium/base/BaseChromiumApplication.java
index 97b2ab49a803293c50911add5a6bc8891ea5a650..1c969c279cd984effdd3a83fbe4c1c4fd82894a5 100644
--- a/base/android/java/src/org/chromium/base/BaseChromiumApplication.java
+++ b/base/android/java/src/org/chromium/base/BaseChromiumApplication.java
@@ -4,17 +4,85 @@
 
 package org.chromium.base;
 
+import android.app.Activity;
 import android.app.Application;
+import android.os.Bundle;
+import android.view.Window;
 
 /**
  * Basic application functionality that should be shared among all browser applications.
  */
 public class BaseChromiumApplication extends Application {
+    /**
+     * Interface to be implemented by listeners for window focus events.
+     */
+    public interface WindowFocusChangedListener {
+        /**
+         * Called when the window focus changes for {@code activity}.
+         * @param activity The {@link Activity} that has a window focus changed event.
+         * @param hasFocus Whether or not {@code activity} gained or lost focus.
+         */
+        public void onWindowFocusChanged(Activity activity, boolean hasFocus);
+    }
+
+    private ObserverList<WindowFocusChangedListener> sWindowFocusListeners =
+            new ObserverList<WindowFocusChangedListener>();
 
     @Override
     public void onCreate() {
         super.onCreate();
         ActivityStatus.initialize(this);
+
+        registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {
+            @Override
+            public void onActivityCreated(final Activity activity, Bundle savedInstanceState) {
+                Window.Callback callback = activity.getWindow().getCallback();
+                activity.getWindow().setCallback(new WindowCallbackWrapper(callback) {
+                    @Override
+                    public void onWindowFocusChanged(boolean hasFocus) {
+                        super.onWindowFocusChanged(hasFocus);
+
+                        for (WindowFocusChangedListener listener : sWindowFocusListeners) {
+                            listener.onWindowFocusChanged(activity, hasFocus);
+                        }
+                    }
+                });
+            }
+
+            @Override
+            public void onActivityDestroyed(Activity activity) { }
+
+            @Override
+            public void onActivityPaused(Activity activity) { }
+
+            @Override
+            public void onActivityResumed(Activity activity) { }

[Ted C, 2014/02/13 04:38:44]

I would add some asserts in a couple of these methods to ensure no one has
overridden the window callbacks with something you don't expect.

Right now, there is nothing to keep someone from calling the setCallback and us
never hearing about window focus again.

[David Trainor- moved to gerrit, 2014/02/13 05:03:55]

Ah yes I forgot about this!  Good idea.

[David Trainor- moved to gerrit, 2014/02/14 19:13:36]

Done.

+
+            @Override
+            public void onActivitySaveInstanceState(Activity activity, Bundle outState) { }
+
+            @Override
+            public void onActivityStarted(Activity activity) { }
+
+            @Override
+            public void onActivityStopped(Activity activity) { }
+
+        });
     }
 
+    /**
+     * Registers a listener to receive window focus updates on activities in this application.
+     * @param listener Listener to receive window focus events.
+     */
+    public void registerWindowFocusChangedListener(WindowFocusChangedListener listener) {
+        sWindowFocusListeners.addObserver(listener);
+    }
+
+    /**
+     * Unregisters a listener from receiving window focus updates on activities in this application.
+     * @param listener Listener that doesn't want to receive window focus events.
+     */
+    public void unregisterWindowFocusChangedListener(WindowFocusChangedListener listener) {
+        sWindowFocusListeners.removeObserver(listener);
+    }
 }