Tweak our JavaScript rewrites a bit to handle jspb.* imports.
diff --git a/js/commonjs/rewrite_tests_for_commonjs.js b/js/commonjs/rewrite_tests_for_commonjs.js
index b6d90d2..82eef18 100644
--- a/js/commonjs/rewrite_tests_for_commonjs.js
+++ b/js/commonjs/rewrite_tests_for_commonjs.js
@@ -80,6 +80,8 @@
   if (isRequire) {
     if (module) {  // Skip goog.require() lines before the first directive.
       var fullSym = isRequire[1];
+      // Skip lines importing from jspb.*, these are handled by the header above.
+      if (fullSym.match(/^jspb\./)) return;
       var sym = tryStripPrefix(fullSym, pkg);
       console.log("googleProtobuf.exportSymbol('" + fullSym + "', " + module + sym + ', global);');
     }