Increase the visibility of the static methods in FirebaseTest (#460)

Author: dconeybe

testing/test_framework/src/firebase_test_framework.h

@@ -236,6 +236,10 @@ class FirebaseTest : public testing::Test {
   // fully-automated tests should be run.
   bool AreInteractiveTestsAllowed();
 
+  // Give the static helper methods "public" visibility so that they can be used
+  // by helper functions defined outside of subclasses of `FirebaseTest`, such
+  // as functions defined in anonymous namespaces.
+ public:
   // Get a persistent string value that was previously set via
   // SetPersistentString. Returns true if the value was set, false if not or if
   // something went wrong.