PM: New (stub) policy for whether an update can be applied.

There's no implementation for this policy yet, and so it always returns
true.

BUG=chromium:358323
TEST=Unit tests.

Change-Id: Id3a0d13cf8c2e9061b800b114d8476c11f998df0
Reviewed-on: https://chromium-review.googlesource.com/197376
Reviewed-by: Gilad Arnold <garnold@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>
Tested-by: Gilad Arnold <garnold@chromium.org>
diff --git a/policy_manager/mock_policy.h b/policy_manager/mock_policy.h
index e46b5bf..118a24b 100644
--- a/policy_manager/mock_policy.h
+++ b/policy_manager/mock_policy.h
@@ -22,6 +22,10 @@
                      EvalStatus(EvaluationContext*, State*, std::string*,
                                 bool*));
 
+  MOCK_CONST_METHOD4(UpdateDownloadAndApplyAllowed,
+                     EvalStatus(EvaluationContext*, State*, std::string*,
+                                bool*));
+
 private:
   DISALLOW_COPY_AND_ASSIGN(MockPolicy);
 };