PolicyManager: Include the Polling interval for kVariableModePoll variables.

A kVariableModePoll variable requires to be polled to know the if the
value changed. This patch adds a new GetPollInterval method that
tells how often a kVariableModePoll variable should be polled. This
value will be used by the policy manager to trigger re-evaluations
of the same policy request.

BUG=chromium:341209
TEST=unit tests added and passes.

Change-Id: I9c982ec8106ce39a0bc0889df7686add131b3bea
Reviewed-on: https://chromium-review.googlesource.com/187703
Reviewed-by: Gilad Arnold <garnold@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
diff --git a/policy_manager/variable_unittest.cc b/policy_manager/variable_unittest.cc
index e346c0d..5d3b8d9 100644
--- a/policy_manager/variable_unittest.cc
+++ b/policy_manager/variable_unittest.cc
@@ -6,6 +6,7 @@
 
 #include "update_engine/policy_manager/variable.h"
 
+using base::TimeDelta;
 using std::string;
 
 namespace chromeos_policy_manager {
@@ -16,6 +17,8 @@
  public:
   DefaultVariable(const string& name, VariableMode mode)
       : Variable<T>(name, mode) {}
+  DefaultVariable(const string& name, const TimeDelta& poll_interval)
+      : Variable<T>(name, poll_interval) {}
   virtual ~DefaultVariable() {}
 
  protected:
@@ -40,4 +43,17 @@
   EXPECT_EQ(other_var.GetMode(), kVariableModePoll);
 }
 
+TEST(PmBaseVariableTest, DefaultPollIntervalTest) {
+  DefaultVariable<int> const_var("const_var", kVariableModeConst);
+  EXPECT_EQ(const_var.GetPollInterval(), TimeDelta());
+  DefaultVariable<int> poll_var("poll_var", kVariableModePoll);
+  EXPECT_EQ(poll_var.GetPollInterval(), TimeDelta::FromMinutes(5));
+}
+
+TEST(PmBaseVariableTest, GetPollIntervalTest) {
+  DefaultVariable<int> var("var", TimeDelta::FromMinutes(3));
+  EXPECT_EQ(var.GetMode(), kVariableModePoll);
+  EXPECT_EQ(var.GetPollInterval(), TimeDelta::FromMinutes(3));
+}
+
 }  // namespace chromeos_policy_manager