PM: Make header guards comply with Google style.

BUG=None
TEST=None

Change-Id: I5cdbddb5233e5408a6e5b6d511b2e2e06a2a566c
Reviewed-on: https://chromium-review.googlesource.com/189209
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/generic_variables.h b/policy_manager/generic_variables.h
index 48764f1..f874b3b 100644
--- a/policy_manager/generic_variables.h
+++ b/policy_manager/generic_variables.h
@@ -6,8 +6,8 @@
 // used by any state provider to implement simple variables to avoid repeat the
 // same common code on different state providers.
 
-#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_POLICY_MANAGER_GENERIC_VARIABLES_H
-#define CHROMEOS_PLATFORM_UPDATE_ENGINE_POLICY_MANAGER_GENERIC_VARIABLES_H
+#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_POLICY_MANAGER_GENERIC_VARIABLES_H_
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_POLICY_MANAGER_GENERIC_VARIABLES_H_
 
 #include "update_engine/policy_manager/variable.h"
 
@@ -61,4 +61,4 @@
 
 }  // namespace chromeos_policy_manager
 
-#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_POLICY_MANAGER_GENERIC_VARIABLES_H
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_POLICY_MANAGER_GENERIC_VARIABLES_H_