Add vpython hook and spec to V8 checkout

R=machenbach@chromium.org

Bug: chromium:777345
Change-Id: I26e4b3e05d84bf5310178aeb5083118567534979
Reviewed-on: https://chromium-review.googlesource.com/735482Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Sergiy Byelozyorov <sergiyb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48874}

.vpython

+# This is a vpython "spec" file.
+#
+# It describes patterns for python wheel dependencies of the python scripts in
+# the chromium repo, particularly for dependencies that have compiled components
+# (since pure-python dependencies can be easily vendored into third_party).
+#
+# When vpython is invoked, it finds this file and builds a python VirtualEnv,
+# containing all of the dependencies described in this file, fetching them from
+# CIPD (the "Chrome Infrastructure Package Deployer" service). Unlike `pip`,
+# this never requires the end-user machine to have a working python extension
+# compilation environment. All of these packages are built using:
+#   https://chromium.googlesource.com/infra/infra/+/master/infra/tools/dockerbuild/
+#
+# All python scripts in the repo share this same spec, to avoid dependency
+# fragmentation.
+#
+# If you have depot_tools installed in your $PATH, you can invoke python scripts
+# in this repo by running them as you normally would run them, except
+# substituting `vpython` instead of `python` on the command line, e.g.:
+#   vpython path/to/script.py some --arguments
+#
+# Read more about `vpython` and how to modify this file here:
+#   https://chromium.googlesource.com/infra/infra/+/master/doc/users/vpython.md
+
+python_version: "2.7"
+
+wheel: <
+  name: "infra/python/wheels/psutil/${vpython_platform}"
+  version: "version:5.2.2"
+>

DEPS

@@ -311,4 +311,14 @@ hooks = [
     'pattern': '.',
     'action': ['python', 'v8/gypfiles/gyp_v8', '--running-as-hook'],
   },
+  # Download and initialize "vpython" VirtualEnv environment packages.
+  {
+    'name': 'vpython_common',
+    'pattern': '.',
+    'condition': 'checkout_android',
+    'action': [ 'vpython',
+                '-vpython-spec', 'v8/.vpython',
+                '-vpython-tool', 'install',
+    ],
+  },
 ]