observation must reset before invoking callbacks

To explain: the problem is that if the side-effect of a callback adds an object which is then mutated, if the reset() comes after the mutation, then no change record is delivered.

R=arv
BUG=https://github.com/Polymer/TemplateBinding/issues/161

Review URL: https://codereview.appspot.com/69860043
Remove unneeded tests for change record type names

The new change record type names and full Array.observe implementation have made it to Stable and there should be no running browsers with the old code

R=arv
BUG=

Review URL: https://codereview.appspot.com/73220043
fix benchmarks

R=arv
BUG=

Review URL: https://codereview.appspot.com/76130043
only check for is object on instance (not prototype)

R=arv
BUG=

Review URL: https://codereview.appspot.com/77090043
initial expressionobserver
fixes
apparently check gets called even when closed...