Exempt code containing goog.base from wrapper.

When @provideGoog is in the code, that is a sign that the user sent JS prefixed with the goog.base code and they don't need the loadModule wrapper.

lib/googmodule.js

@@ -1,16 +1,22 @@
 var path = require('path');
 
+// If the code has goog.module we need to wrap it.
 var MODULE_REGEXP = /(^|;)\s*goog\.module\s*\(\s*['""]/m;
+// If the code already has goog.base no wrapper even if goog.module.
+var GOOGBASE_REGEXP = /^ \* @provideGoog *$/m;
 
 var createPreprocesor = function(logger, /* config.basePath */ basePath) {
   var log = logger.create('preprocessor.googmodule');
 
   return function(content, file, done) {
-    if (path.extname(file.originalPath) !== '.js' ||
-        // Only check the first 10k chars, for performance reasons, to avoid
-        // degenerate behaviour on very large JS files. That's enough to allow
-        // for the Apache license, docs, and similar headers.
-        !MODULE_REGEXP.test(content.substring(0, 10000))) {
+    if (path.extname(file.originalPath) !== '.js') {
+      return done(content);
+    }
+    // Only check the first 10k chars, for performance reasons, to avoid
+    // degenerate behaviour on very large JS files. That's enough to allow
+    // for the Apache license, docs, and similar headers.
+    var first10k = content.substring(0, 10000);
+    if (!MODULE_REGEXP.test(first10k) || GOOGBASE_REGEXP.test(first10k) {
       return done(content);
     }