The flag for deactivating break points also affects stepping, since both
are implemented via debug break slots. Fixing this by introducing a new
flag solely responsible for deactivating actual break points.

R=mvstanton@chromium.org
BUG=chromium:119800
LOG=N

Review URL: https://codereview.chromium.org/1402913002

Cr-Commit-Position: refs/heads/master@{#31236}