Add support for typed heaps on trunk.

With oilpan we support segregating allocation into different heap pages based on the type. This change adds the remaining code to trunk to support this.
There is a simple test which allocates two small objects and checks they are not on the same heap page. Given that the allocation is of small objects they would have been on the same page in the case where there is no segregation.

I also added the isMarked method to the visitor and modified a test to use it. It was mainly to match what was supported for typed heaps.

R=ager@chromium.org, cevans@chromium.org, erik.corry@gmail.com, haraken@chromium.org, vegorov@chromium.org, zerny@chromium.org
BUG=

Review URL: https://codereview.chromium.org/128103002

git-svn-id: svn://svn.chromium.org/blink/trunk@164684 bbb929c8-8fbe-4397-9dbb-9b2b20218538