PolicyManager: Mark protected members as private.

The Google C++ style guide requires members to be private having
a getter and setter with fixed names. This patch moves the protected
members to the private section on the base class for each provider
and adds a protected setter to allow the sub-classes to set these
members on Init().

Also, this patch uniforms the variable names prefixing them with
var_.

BUG=None
TEST=Unit tests still passes.

Change-Id: I4cbf7b7031b430991c12a5c7d9729bafaf359095
Reviewed-on: https://chromium-review.googlesource.com/187979
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/random_provider.h b/policy_manager/random_provider.h
index fcc4889..f921073 100644
--- a/policy_manager/random_provider.h
+++ b/policy_manager/random_provider.h
@@ -19,15 +19,19 @@
   // returned 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.
-  Variable<uint64_t>* seed() const { return seed_.get(); }
+  Variable<uint64_t>* var_seed() const { return var_seed_.get(); }
 
  protected:
   RandomProvider() {}
 
-  // The seed() scoped variable.
-  scoped_ptr<Variable<uint64_t> > seed_;
+  void set_var_seed(Variable<uint64_t>* var_seed) {
+    var_seed_.reset(var_seed);
+  }
 
  private:
+  // The seed() scoped variable.
+  scoped_ptr<Variable<uint64_t>> var_seed_;
+
   DISALLOW_COPY_AND_ASSIGN(RandomProvider);
 };