AndroidOverlay implementation using Dialog.

ui/android/java/src/org/chromium/ui/base/WindowAndroid.java

 // Copyright 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.ui.base;
 
 import android.animation.Animator;
 import android.animation.AnimatorListenerAdapter;
 import android.annotation.SuppressLint;
 import android.annotation.TargetApi;
 import android.app.Activity;
 import android.app.PendingIntent;
 import android.content.Context;
 import android.content.ContextWrapper;
 import android.content.Intent;
 import android.content.pm.PackageManager;
 import android.os.Build;
 import android.os.Bundle;
+import android.os.IBinder;
 import android.os.Process;
 import android.util.Log;
 import android.util.SparseArray;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.accessibility.AccessibilityManager;
 
 import org.chromium.base.ApiCompatibilityUtils;
 import org.chromium.base.Callback;
 import org.chromium.base.ObserverList;
@@ skipping 690 matching lines @@
      * Getter for the current context (not necessarily the application context).
      * Make no assumptions regarding what type of Context is returned here, it could be for example
      * an Activity or a Context created specifically to target an external display.
      */
     public WeakReference<Context> getContext() {
         // Return a new WeakReference to prevent clients from releasing our internal WeakReference.
         return new WeakReference<>(mContextRef.get());
     }
 
     /**
+     * Return the current window token, or null.
+     */
+    @CalledByNative
+    private IBinder getWindowToken() {
+        Context context = mContextRef.get();
+        if (context == null) return null;

[boliu, 2017/03/30 22:42:02]

this check not needed, activityFromContext should return null if you pass it
null

[liberato (no reviews please), 2017/04/04 17:49:28]

Done.

+        Activity activity = activityFromContext(context);
+        if (activity == null) return null;
+        View decorView = activity.getWindow().peekDecorView();

[boliu, 2017/03/30 22:42:02]

actually need null check for getWindow? docs says
"Window The current window, or null if the activity is not visual."

[liberato (no reviews please), 2017/04/04 17:49:28]

unclear.  i'll add it.

+        if (decorView == null) return null;
+        return decorView.getWindowToken();
+    }
+
+    /**
      * Update whether the placeholder is 'drawn' based on whether an animation is running
      * or touch exploration is enabled - if either of those are true, we call
      * setWillNotDraw(false) to ensure that the animation is drawn over the SurfaceView,
      * and otherwise we call setWillNotDraw(true).
      */
     private void refreshWillNotDraw() {
         boolean willNotDraw = !mIsTouchExplorationEnabled && mAnimationsOverContent.isEmpty();
         if (mAnimationPlaceholderView.willNotDraw() != willNotDraw) {
             mAnimationPlaceholderView.setWillNotDraw(willNotDraw);
         }
@@ skipping 14 matching lines @@
     private native void nativeOnVSync(long nativeWindowAndroid,
                                       long vsyncTimeMicros,
                                       long vsyncPeriodMicros);
     private native void nativeOnVisibilityChanged(long nativeWindowAndroid, boolean visible);
     private native void nativeOnActivityStopped(long nativeWindowAndroid);
     private native void nativeOnActivityStarted(long nativeWindowAndroid);
     private native void nativeSetVSyncPaused(long nativeWindowAndroid, boolean paused);
     private native void nativeDestroy(long nativeWindowAndroid);
 
 }