Cherry-pick: [Android WebView] Null check syncOnNewPictureStateToNative

Cherry-pick of Chromium crrev.com/r233453

BUG: 11555111

Original description:

Make sure we don't call into native after the native pointer has been
destroyed.

Change-Id: Id0321a74656fd5a83d3e82115638e65c08531a10
1 file changed