Replace WindowCallbackWrapper with a generated instance.

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 2946f6fb0004ad2da54e4e5985f4f75029ff2901..c87d02d7d33e8fbee7b44f87472af8af74d8973e 100644
--- a/base/android/java/src/org/chromium/base/BaseChromiumApplication.java
+++ b/base/android/java/src/org/chromium/base/BaseChromiumApplication.java
@@ -11,6 +11,10 @@ import android.os.Bundle;
 import android.view.KeyEvent;
 import android.view.Window;
 
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+
 /**
  * Basic application functionality that should be shared among all browser applications.
  */
@@ -30,66 +34,94 @@ public class BaseChromiumApplication extends Application {
     private ObserverList<WindowFocusChangedListener> mWindowFocusListeners =
             new ObserverList<WindowFocusChangedListener>();
 
+    /**
+     * Intercepts calls to an existing Window.Callback. Most invocations are passed on directly
+     * to the composed Window.Callback but enables intercepting/manipulating others.
+     *
+     * This is used to relay window focus changes throughout the app and remedy a bug in the
+     * appcompat library.
+     */
+    private class WindowCallbackProxy implements InvocationHandler {
+        private final Window.Callback mCallback;
+        private final Activity mActivity;
+
+        public WindowCallbackProxy(Activity activity, Window.Callback callback) {
+            mCallback = callback;
+            mActivity = activity;
+        }
+
+        @Override
+        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
+            if (method.getName().equals("onWindowFocusChanged") && args.length == 1
+                    && args[0] instanceof Boolean) {
+                onWindowFocusChanged((boolean) args[0]);
+                return null;
+            } else if (method.getName().equals("dispatchKeyEvent") && args.length == 1
+                    && args[0] instanceof KeyEvent) {
+                return dispatchKeyEvent((KeyEvent) args[0]);
+            } else {
+                return method.invoke(mCallback, args);
+            }
+        }
+
+        public void onWindowFocusChanged(boolean hasFocus) {
+            mCallback.onWindowFocusChanged(hasFocus);
+
+            for (WindowFocusChangedListener listener : mWindowFocusListeners) {
+                listener.onWindowFocusChanged(mActivity, hasFocus);
+            }
+        }
+
+        public boolean dispatchKeyEvent(KeyEvent event) {
+            // TODO(aurimas): remove this once AppCompatDelegateImpl no longer steals
+            // KEYCODE_MENU. (see b/20529185)
+            if (event.getKeyCode() == KeyEvent.KEYCODE_MENU && mActivity.dispatchKeyEvent(event)) {
+                return true;
+            }
+            return mCallback.dispatchKeyEvent(event);
+        }
+    }
     @Override
     public void onCreate() {
         super.onCreate();
         ApplicationStatus.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 : mWindowFocusListeners) {
-                            listener.onWindowFocusChanged(activity, hasFocus);
-                        }
-                    }
-
-                    @Override
-                    public boolean dispatchKeyEvent(KeyEvent event) {
-                        // TODO(aurimas): remove this once AppCompatDelegateImpl no longer steals
-                        // KEYCODE_MENU. (see b/20529185)
-                        if (event.getKeyCode() == KeyEvent.KEYCODE_MENU
-                                && activity.dispatchKeyEvent(event)) {
-                            return true;
-                        }
-                        return super.dispatchKeyEvent(event);
-                    }
-                });
+                activity.getWindow().setCallback((Window.Callback) Proxy.newProxyInstance(
+                        Window.Callback.class.getClassLoader(), new Class[] {Window.Callback.class},
+                        new WindowCallbackProxy(activity, callback)));
             }
 
             @Override
             public void onActivityDestroyed(Activity activity) {
-                assert activity.getWindow().getCallback() instanceof WindowCallbackWrapper;
+                assert Proxy.isProxyClass(activity.getWindow().getCallback().getClass());
             }
 
             @Override
             public void onActivityPaused(Activity activity) {
-                assert activity.getWindow().getCallback() instanceof WindowCallbackWrapper;
+                assert Proxy.isProxyClass(activity.getWindow().getCallback().getClass());
             }
 
             @Override
             public void onActivityResumed(Activity activity) {
-                assert activity.getWindow().getCallback() instanceof WindowCallbackWrapper;
+                assert Proxy.isProxyClass(activity.getWindow().getCallback().getClass());
             }
 
             @Override
             public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
-                assert activity.getWindow().getCallback() instanceof WindowCallbackWrapper;
+                assert Proxy.isProxyClass(activity.getWindow().getCallback().getClass());
             }
 
             @Override
             public void onActivityStarted(Activity activity) {
-                assert activity.getWindow().getCallback() instanceof WindowCallbackWrapper;
+                assert Proxy.isProxyClass(activity.getWindow().getCallback().getClass());
             }
 
             @Override
             public void onActivityStopped(Activity activity) {
-                assert activity.getWindow().getCallback() instanceof WindowCallbackWrapper;
+                assert Proxy.isProxyClass(activity.getWindow().getCallback().getClass());
             }
         });
     }