[IndexedDB] What should be allowed as a key path?

As far as I recall, we never settled on how key path should be specified.
 Right now in Chrome, we allow any combination of .'s and static array
lookups.  So, for example, we allow "foo.bar[1][2].baz".  I don't remember
any specific use cases for the array lookups though, so I'm wondering if we
should just specify "<property> ["." <property>]*" to be the key path
specification.  Where <property> is whatever's allowed in JavaScript.  It
seems to me that this should support most use cases, should be easy to
understand and implement, and should leave us a lot of flexibility to
support other use cases as we may come up with them.

Thoughts?

J