PM: Various fixes to Random Provider

* Remove mention of uint64; use uint64_t instead.

* Simpler reading of bytes from /dev/urandom into a uint64_t.

* Replace string concatenation with StringPrintf.

BUG=None
TEST=Builds and passes unit tests.

Change-Id: Ic0760ae4c2b21e4ffc823a676a9439e867bf9f64
Reviewed-on: https://chromium-review.googlesource.com/184326
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/random_vars.h b/policy_manager/random_vars.h
index d983ca1..f0ed4ed 100644
--- a/policy_manager/random_vars.h
+++ b/policy_manager/random_vars.h
@@ -5,8 +5,6 @@
 #ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_PM_RANDOM_VARS_H
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_PM_RANDOM_VARS_H
 
-#include "base/basictypes.h"
-
 #include "policy_manager/variable.h"
 
 namespace chromeos_policy_manager {
@@ -15,7 +13,7 @@
 // by the variables are cached by the EvaluationContext, so the returned value
 // will be the same during the same policy request. If more random values are
 // needed use a PRNG seeded with this value.
-extern Variable<uint64>* var_random_seed;
+extern Variable<uint64_t>* var_random_seed;
 
 }  // namespace chromeos_policy_manager