Add some missing APIs base.js.

I refactored most other stuff to stop depending base.js but couple of things left that require more work; particularly:
 - goog.global: is used in different places incl. open-source so the refactoring of this is a larger task so better drop it later on.
 - goog.setTestOnly: I don't think there is a compiler level alternative and I didn't want to drop whole from open-source right now without replacemen so postponed any refactorings around it.
 - goog.getObjectByName: we still rely on it though we can probably drop it later on when fully migrate out of globals for System.getProperty.

PiperOrigin-RevId: 718092702

Author: gkdn

lib/base.js

@@ -36,6 +36,21 @@ var COMPILED = false;
 var goog = goog || {};
 
 
+/**
+ * Reference to the global object.
+ * https://www.ecma-international.org/ecma-262/9.0/index.html#sec-global-object
+ *
+ * More info on this implementation here:
+ * https://docs.google.com/document/d/1NAeW4Wk7I7FV0Y2tcUFvQdGMc89k2vdgSXInw8_nvCI/edit
+ *
+ * @const
+ * @suppress {undefinedVars} self won't be referenced unless `this` is falsy.
+ * @type {!Global}
+ * @deprecated Use `globalThis` directly; this version will be deleted.
+ */
+goog.global = globalThis;
+
+
 /**
  * A hook for overriding the define values in uncompiled or compiled mode.
  *
@@ -203,6 +218,12 @@ goog.DEBUG = goog.define('goog.DEBUG', true);
  */
 goog.LOCALE = goog.define('goog.LOCALE', 'en');  // default to en
 
+/**
+ * @define {boolean} Whether code that calls {@link goog.setTestOnly} should
+ *     be disallowed in the compilation unit.
+ */
+goog.DISALLOW_TEST_ONLY_CODE =
+    goog.define('goog.DISALLOW_TEST_ONLY_CODE', COMPILED && !goog.DEBUG);
 
 /**
  * Defines a global namespace in Closure.
@@ -260,7 +281,7 @@ goog.constructNamespace_ = function(name, object, overwriteImplicit) {
 
     var namespace = name;
     while ((namespace = namespace.substring(0, namespace.lastIndexOf('.')))) {
-      if (goog.getObjectByName_(namespace)) {
+      if (goog.getObjectByName(namespace)) {
         break;
       }
       goog.implicitNamespaces_[namespace] = true;
@@ -368,7 +389,7 @@ goog.module.getInternal_ = function(name) {
     if (name in goog.loadedModules_) {
       return goog.loadedModules_[name];
     } else if (!goog.implicitNamespaces_[name]) {
-      var ns = goog.getObjectByName_(name);
+      var ns = goog.getObjectByName(name);
       return ns != null ? ns : null;
     }
   }
@@ -415,6 +436,27 @@ goog.module.declareLegacyNamespace = function() {
 };
 
 
+/**
+ * Marks that the current file should only be used for testing, and never for
+ * live code in production.
+ *
+ * In the case of unit tests, the message may optionally be an exact namespace
+ * for the test (e.g. 'goog.stringTest'). The linter will then ignore the extra
+ * provide (if not explicitly defined in the code).
+ *
+ * @param {string=} opt_message Optional message to add to the error that's
+ *     raised when used in production code.
+ */
+goog.setTestOnly = function(opt_message) {
+  if (goog.DISALLOW_TEST_ONLY_CODE) {
+    opt_message = opt_message || '';
+    throw new Error(
+        'Importing test-only code into non-debug environment' +
+        (opt_message ? ': ' + opt_message : '.'));
+  }
+};
+
+
 /**
  * Forward declares a symbol. This is an indication to the compiler that the
  * symbol may be used in the source yet is not required and may not be provided
@@ -449,7 +491,7 @@ if (!COMPILED) {
   goog.isProvided_ = function(name) {
     return (name in goog.loadedModules_) ||
         (!goog.implicitNamespaces_[name] &&
-         goog.getObjectByName_(name) != null);
+         goog.getObjectByName(name) != null);
   };
 
   /**
@@ -479,9 +521,9 @@ if (!COMPILED) {
  * @param {!Object=} opt_obj The object within which to look; default is
  *     globalThis.
  * @return {?} The value (object or primitive) or, if not found, null.
- * @private
+ * @deprecated Prefer non-reflective access.
  */
-goog.getObjectByName_ = function(name, opt_obj) {
+goog.getObjectByName = function(name, opt_obj) {
   var parts = name.split('.');
   var cur = opt_obj || globalThis;
   for (var i = 0; i < parts.length; i++) {