This moves collection of function information from its previous spot in
the standard compiler pipeline (GetSharedFunctionInfo() and
CompileTopLevel()) to its new location in CompileForLiveEdit. Nesting
information is reconstructed by traversing the AST.

R=yangguo@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/1971683002
Cr-Commit-Position: refs/heads/master@{#36306}