Add a virtualenv-based python bootstrapping service to infra.

README.md

 Contributing to the Chrome infra codebase
 =========================================
 
 This document explains how to contribute to the Chrome infrastructure codebase.
 If you want to contribute to the Chromium browser, you're in the wrong place.
 See
 [http://dev.chromium.org/getting-involved](http://dev.chromium.org/getting-involved)
 instead. You can find more information on the Chrome infrastructure
 [here](http://dev.chromium.org/infra).
 
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 somewhere in your path) to run:
 
     mkdir chrome_infra   # or whatever name you please
     cd chrome_infra
     gclient config https://chromium.googlesource.com/infra/infra.git
     gclient sync
 
 This will check out the base repository (infra/) and its dependencies.
 
 
+Bootstrapping Dependencies
+--------------------------
+(See `bootstrap/README.md` for more details).
+
+Manually create a bootstrap virtualenv environment by running:
+
+  `./bootstrap/bootstrap.py --deps_file bootstrap/deps.pyl`
+
+This is done for you automatically by `gclient sync` (or `gclient runhooks`).
+
+
 Invoking tools
 --------------
 
 Mixing modules and scripts in the same hierarchy can sometimes be a pain in
 Python, because it usually requires updating the Python path. The goal for
 infra/ is to be able to check out the repository and be able to run code right
 away, without setting up anything. The adopted solution is to use __main__.py
 files everywhere.
 
 Example: `python -m infra.services.lkgr_finder` will run the lkgr_finder script.
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   is mirrored on
   [https://chromium.googlesource.com/infra/third_party/httplib2.git](https://chromium.googlesource.com/infra/third_party/httplib2.git))
 - add an entry into infra/DEPS pointing to the mirror, at a given revision
   (not HEAD).
 - add an 'import' entry into `infra/ext/__init__.py`. This is to enable
   autocompletion for tools like pylint and jedi.
 
 The two first steps can only be performed by a limited set of people. Send an
 email to infra-dev@chromium.org to request that.