This is a preparatory change to only use the class in question when
allocating a CompilationInfo on the C-heap for a compilation job. As a
next step we will make CompilationInfoWithZone disappear and make the
CompilationJob be the one C-heap allocated object.

R=bmeurer@chromium.org

Review-Url: https://codereview.chromium.org/1931573003
Cr-Commit-Position: refs/heads/master@{#35848}