DialogSurfaceManager implementation.

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 7fc6180aecdd009f0fe60a5ac36847a175630ead..a03d9ebaddebe3080d4ad53ffac6d13ce33a79b7 100644
--- a/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
+++ b/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
@@ -17,6 +17,7 @@ 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;
@@ -663,6 +664,19 @@ public class WindowAndroid {
     }
 
     /**
+     * Return the current window token, or null.
+     * TODO(liberato): explain this better.  also mention embedders.t d
+     */
+    public IBinder getWindowToken() {
+        Context context = mContextRef.get();
+        if (context == null) return null;
+        Activity activity = activityFromContext(context);
+        if (activity == null) return null;
+
+        return activity.getWindow().getDecorView().getRootView().getWindowToken();

[boliu, 2016/11/14 16:39:25]

peekDecorView might be safer, but need a null check

is getRootView required?

[liberato (no reviews please), 2016/12/20 17:16:38]

peekDecorView: done.
getRootView: now that you mention it, i don't think so.  i'll check and remove
if not.

+    }
+
+    /**
      * 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,