Removes the SharedFunctionInfo field from the ParseInfo structure. Instead
require a SharedFunctionInfo to be explicitly passed to ParseFunction.
Also renames GetUnoptimizedCode to CompileUnoptimizedFunction to make it
clear it should only be called for non-top-level code.

BUG=v8:5203

Change-Id: Ibce016e6a5290c3685f7f0a2f5fb1eb2df2ffc3b
Reviewed-on: https://chromium-review.googlesource.com/574589
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46814}