[Oilpan]: Make sure our compile asserts in vector are called.

We missed the compile assert in the VectorDestructor's clear method when having vectors where elements were only added.
This should fix that. It also caught a few places where we had to define a new trait.

R=ager@chromium.org, erik.corry@gmail.com, haraken@chromium.org, oilpan-reviews@chromium.org, tkent@chromium.org, vegorov@chromium.org, zerny@chromium.org
BUG=

Review URL: https://codereview.chromium.org/219243003

git-svn-id: svn://svn.chromium.org/blink/trunk@170526 bbb929c8-8fbe-4397-9dbb-9b2b20218538