After updating to Android System WebView (version 62.0.3202.84), if admob banner refreshes itself during a drag action on another view, this bug occurs when the view is dropped:

java.lang.NullPointerException: 
  at org.chromium.android_webview.AwContents$AwViewMethodsImpl.onDragEvent (AwContents.java:191)
  at com.android.webview.chromium.WebViewChromium.onDragEvent (WebViewChromium.java:782)
  at android.webkit.WebView.onDragEvent (WebView.java:2554)
  at android.view.View.dispatchDragEvent (View.java:22202)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1431)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewGroup.dispatchDragEvent (ViewGroup.java:1417)
  at android.view.ViewRootImpl.handleDragEvent (ViewRootImpl.java:6308)
  at android.view.ViewRootImpl.-wrap11 (ViewRootImpl.java)
  at android.view.ViewRootImpl$ViewRootHandler.handleMessage (ViewRootImpl.java:4199)
  at android.os.Handler.dispatchMessage (Handler.java:102)
  at android.os.Looper.loop (Looper.java:154)
  at android.app.ActivityThread.main (ActivityThread.java:6776)
  at java.lang.reflect.Method.invoke (Native Method)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run (ZygoteInit.java:1496)
  at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:1386)

You can reproduce it in these steps:
- create an activity with an adbanner on bottom, having frequency update = optimized by google
- start a drag on a view (contained in the activity) and keep view dragged until banner refresh
- drop view
- app freezes with that stacktrace

cloned from AOSP bug b/69347400