In order to compile eager inner functions on a background thread we need to
keep the handles created during parsing and scope analysis alive until the
background compilation is complete. In order to do that, we allocate the
handles in a deferred handle scope and keep the deferred handles alive with
a shared_ptr in the ParseInfo and CompileInfo respectively.

BUG=v8:5203

Review-Url: https://codereview.chromium.org/2650883002
Cr-Commit-Position: refs/heads/master@{#43091}