Fix testFlattenPinAllDeps

This needs an update after simultaneous landing of
https://chromium-review.googlesource.com/c/561681/ and
https://chromium-review.googlesource.com/c/562138/ .

TBR=dpranke

Bug: 570091
Change-Id: I35ba4fa95ee97a8059eedf5ebf13b09b1c5ee89c
Reviewed-on: https://chromium-review.googlesource.com/563196
Reviewed-by: Paweł Hajdan Jr. <phajdan.jr@chromium.org>
Commit-Queue: Paweł Hajdan Jr. <phajdan.jr@chromium.org>

tests/gclient_smoketest.py

@@ -838,6 +838,12 @@ class GClientSmokeGIT(GClientSmokeBase):
         '',
         '}',
         '',
+        'vars = {',
+        '  # src',
+        '  "DummyVariable": \'repo\',',
+        '',
+        '}',
+        '',
     ], deps_contents.splitlines())