Remove SnapshotFillerInterface

There used to be additional pass in the heap profiler that estimated memory required for the snapshot and it used special implementation of the interface. Now that we dropped that step it doesn't makes sense to keep the interface with single implementation.

BUG=None
LOG=N
R=loislo@chromium.org, mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/194503002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19875 ce2b1a6d-e550-0410-aec6-3dcde31c8c00