A64: Record the size of veneer pools for code offset mapping.

Mapping the code offsets between code with and without debug break slots
requires information about the size of the veneer pools and constant pools.

BUG=v8:3173
LOG=N
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/188253005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19857 ce2b1a6d-e550-0410-aec6-3dcde31c8c00