This is a pure refactoring and renaming of methods in the compiler API
with the goal to increase readability. Also the compiler API is moved to
the top of the file, as it is the central piece in that file.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/1766623004

Cr-Commit-Position: refs/heads/master@{#34579}