Fix Blockly.utils.global when wrapped in a module. (#3035)

* Fix Blockly.utils.global when wrapped in a module.

.eslintignore

@@ -4,6 +4,7 @@ blockly_node_javascript_en.js
 gulpfile.js
 /msg/*
 /core/css.js
+/core/utils/global.js
 /tests/blocks/*
 /tests/compile/*
 /tests/jsunit/*

core/utils/global.js

@@ -19,7 +19,7 @@
  */
 
 /**
- * @fileoverview Core utility methods for Blockly
+ * @fileoverview Provides a reference to the global object.
  * @author samelh@google.com (Sam El-Husseini)
  */
 'use strict';
@@ -33,6 +33,19 @@ goog.provide('Blockly.utils.global');
 
 /**
  * Reference to the global object.
+ *
+ * More info on this implementation here:
+ * https://docs.google.com/document/d/1NAeW4Wk7I7FV0Y2tcUFvQdGMc89k2vdgSXInw8_nvCI/edit
  */
-Blockly.utils.global = this || self;
-
+Blockly.utils.global = function() {
+  if (typeof self === 'object') {
+    return self;
+  }
+  if (typeof window === 'object') {
+    return window;
+  }
+  if (typeof global === 'object') {
+    return global;
+  }
+  return this;
+}();

gulpfile.js

@@ -509,8 +509,6 @@ function packageCommonJS(namespace, dependencies) {
  */
 gulp.task('package-blockly', function() {
   return gulp.src('blockly_compressed.js')
-    .pipe(gulp.insert.prepend(`
-    var self = this;`))
     .pipe(packageUMD('Blockly', []))
     .pipe(gulp.rename('blockly.js'))
     .pipe(gulp.dest(packageDistribution));
@@ -524,9 +522,8 @@ gulp.task('package-blockly', function() {
 gulp.task('package-blockly-node', function() {
   // Override textToDomDocument, providing a Node.js alternative to DOMParser.
   return gulp.src('blockly_compressed.js')
-    .pipe(gulp.insert.wrap(`
-    var self = global;`,
-      `if (typeof DOMParser !== 'function') {
+    .pipe(gulp.insert.append(`
+      if (typeof DOMParser !== 'function') {
         var JSDOM = require('jsdom').JSDOM;
         var window = (new JSDOM()).window;
         var document = window.document;