Since gclient knows what the correct DEPS are, it SHOULD be managing the .git/info/exclude file (or at least a subset of it) in the repo. Right now we are duplicating DEPS into .gitignore manually, which is just a bad idea:
  * it can hold stale values, leaving folders on the bot that should be deleted
  * it can be accidentally not updated, causing gclient to delete folders that it shouldn't.
  * it's annoying

Would have prevented  issue 690010 .

Proposal is that when you `gclient sync` it reads the current exclude file, parses out two comment guards, e.g. 

### vvvvv   GCLIENT MANAGED   vvvvvv
stuff
### ^^^^^   GCLIENT MANAGED   ^^^^^^

and replaces those lines with an updated set of ignore statements, one per DEPS entry which is intended to sync. It then proceeds with the sync as normal.

After this is implemented, we should remove the bogus entries in the various .gitignore files around chromium/src.