PM: Policy for checking whether an update may use the current connection.

This is based on logic currently found in
ConnectionManager::IsUpdateAllowedOver() and
LibcurlHttpFetcher::IsUpdateAllowedOverCurrentConnection().

BUG=chromium:358323
TEST=Unit tests.

Change-Id: Ib1a73d3fbe603b8686294088e26bc2d04ee73877
Reviewed-on: https://chromium-review.googlesource.com/199540
Tested-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>
diff --git a/policy_manager/default_policy.h b/policy_manager/default_policy.h
index 56eedf2..1e2a471 100644
--- a/policy_manager/default_policy.h
+++ b/policy_manager/default_policy.h
@@ -44,6 +44,15 @@
     return EvalStatus::kSucceeded;
   }
 
+  virtual EvalStatus UpdateCurrentConnectionAllowed(
+      EvaluationContext* ec,
+      State* state,
+      std::string* error,
+      bool* result) const override {
+    *result = true;
+    return EvalStatus::kSucceeded;
+  }
+
  private:
   DISALLOW_COPY_AND_ASSIGN(DefaultPolicy);
 };