Fix invalid test, fast/dom/wrapper-classes.html

The test incorrectly tested that the [[Class]] of the constructor was
set to "FooConstructor", it should be se to "Foo".

Note that we still, fail the [[Class]] tests for Foo.prototype.

BUG=239175

Review URL: https://chromiumcodereview.appspot.com/22594004

git-svn-id: svn://svn.chromium.org/blink/trunk@155863 bbb929c8-8fbe-4397-9dbb-9b2b20218538