Oilpan: Remove Document* pointers in objects

This CL replaces Document* pointers in objects with Member<Document>s.

- Move TextAutosizer to oilpan's heap.
- Move FastTextAutosizer to oilpan's heap.
- Make FastBulider STACK_ALLOCATED.
- Make ViewportStyleResolver::m_document a Member.

BUG=340522

Review URL: https://codereview.chromium.org/420273005

git-svn-id: svn://svn.chromium.org/blink/trunk@179066 bbb929c8-8fbe-4397-9dbb-9b2b20218538