Add tests for array length bounds in WebView's Java Bridge

Tests for https://android-git.corp.google.com/g/150320.

We test that when the legnth property of a JavaScript object is out of the
bounds for a Java array, we convert to null.

Also update a test in the case that the length property is not numeric.

Bug: 5626284
Change-Id: If41acb117eb4b786d671b5ffece2704c6f045d52