While at it, remove the notion of INTERNAL variables.
@caitp: Took some parts from your CL, since I was blocked on the temp scope bug.
R=mstarzinger@chromium.org
BUG=512574
LOG=N
Review URL: https://codereview.chromium.org/1250513004
Cr-Commit-Position: refs/heads/master@{#29812}
