AndroidOverlay implementation using Dialog.

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

Index: ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
diff --git a/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java b/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
index d9771f74edd7707bc3043936bc23f221dfcc358f..2ab71e157974687daed7be040c82208229c8c99a 100644
--- a/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
+++ b/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
@@ -16,6 +16,7 @@ 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;
@@ -726,6 +727,20 @@ public class WindowAndroid {
     }
 
     /**
+     * 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,