fix(core): add file check script in travis build

Author: JiaLiPassion

Diff for: check-file-size.js

@@ -0,0 +1,27 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+const fs = require('fs');
+
+module.exports = function(config) {
+  let chkResult = true;
+  config.targets.forEach(target => {
+    if (target.checkTarget) {
+      try {
+        const stats = fs.statSync(target.path);
+        if (stats.size > target.limit) {
+          console.error(`file ${target.path} size over limit, limit is ${target.limit}, actual is ${stats.size}`);
+          chkResult = false;
+        }
+      } catch (err) {
+        console.error(`failed to get filesize: ${target.path}`);
+        chkResult = false;
+      }
+    }
+  });
+  return chkResult;
+};

Diff for: file-size-limit.json

@@ -0,0 +1,9 @@
+{
+  "targets": [
+    {
+      "path": "dist/zone.min.js",
+      "checkTarget": true,
+      "limit": 40000
+    }
+  ]
+}

Diff for: gulpfile.js

@@ -410,3 +410,14 @@ gulp.task('promisetest', ['build/zone-node.js'], (cb) => {
       }
     });
 });
+
+// check dist file size limitation
+gulp.task('filesize', ['build'], (cb) => {
+    const checker = require('./check-file-size');
+    const result = checker(require('./file-size-limit.json'));
+    if (result) {
+      cb();
+    } else {
+      cb('check file size failed');
+    }
+});