[DEPS] Seed vpython environments on checkout.

Use vpython's "install" subcommand to ensure that all of the necessary
VirtualEnv packages are local to the developer/system on sync rather
than on-demand. This will enable better offline support by removing the
possibility that a package download needs to happen after runhooks step.

BUG=None
TEST=local
  - Ran "runhooks" locally.

Change-Id: Iddb491d31ea64211cc304fda1112eb957a8fe047
Reviewed-on: https://chromium-review.googlesource.com/713094
Reviewed-by: Quinten Yearsley <[email protected]>
Reviewed-by: Dirk Pranke <[email protected]>
Commit-Queue: Daniel Jacques <[email protected]>
Cr-Commit-Position: refs/heads/master@{#508449}
diff --git a/DEPS b/DEPS
index 4f318a7..5a8243f 100644
--- a/DEPS
+++ b/DEPS
@@ -1387,6 +1387,24 @@
       'bb7a8c4be8001868468ba0a76389ce4ee111620c',
     ],
   },
+
+  # Download and initialize "vpython" VirtualEnv environment packages.
+  {
+    'name': 'vpython_common',
+    'pattern': '.',
+    'action': [ 'vpython',
+                '-vpython-spec', 'src/.vpython',
+                '-vpython-tool', 'install',
+    ],
+  },
+  {
+    'name': 'vpython_webkitpy',
+    'pattern': '.',
+    'action': [ 'vpython',
+                '-vpython-spec', 'src/third_party/WebKit/Tools/Scripts/common.vpython',
+                '-vpython-tool', 'install',
+    ],
+  },
 ]
 
 recursedeps = [