Move private APIs to private namespace

Fixes #2078

spec/html/SpyRegistryHtmlSpec.js

@@ -1,11 +1,11 @@
 describe('Spy Registry browser-specific behavior', function() {
   function createSpy(name, originalFn) {
-    return jasmineUnderTest.Spy(name, originalFn);
+    return privateUnderTest.Spy(name, originalFn);
   }
 
   it('can spy on and unspy window.onerror', function() {
     const spies = [],
-      spyRegistry = new jasmineUnderTest.SpyRegistry({
+      spyRegistry = new privateUnderTest.SpyRegistry({
         currentSpies: function() {
           return spies;
         },