The current usage pattern is always to allocate a {ModuleCompiler}, then
call {CompileToModuleObject}, then deallocate the {ModuleCompiler}.
Hence, the method can be made static and allocate the {ModuleCompiler}
internally.
This also gives back a reason for the existence of
{CompileToModuleObjectInternal}.

R=ahaas@chromium.org

Change-Id: Iac1ba28421ade6728046c0b9a6e9fc249a349491
Reviewed-on: https://chromium-review.googlesource.com/650386Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47834}