Creating helper methods for the setTimeout uses

Abstracting out some of the setTimeout patterns that have popped up in
the code to make the intention clearer.

src/js/parser/javascript.js

@@ -1,6 +1,7 @@
 import Snap from 'snapsvg';
 import _ from 'lodash';
 
+import util from '../util.js';
 import javascript from './javascript/parser.js';
 import ParserState from './javascript/parser_state.js';
 
@@ -46,18 +47,11 @@ export default class Parser {
   parse(expression) {
     this._addClass('loading');
 
-    return new Promise((resolve, reject) => {
-      setTimeout(() => {
-        try {
-          javascript.Parser.SyntaxNode.state = this.state;
+    return util.tick().then(() => {
+      javascript.Parser.SyntaxNode.state = this.state;
 
-          this.parsed = javascript.parse(expression.replace(/\n/g, '\\n'));
-          resolve(this);
-        }
-        catch(e) {
-          reject(e);
-        }
-      });
+      this.parsed = javascript.parse(expression.replace(/\n/g, '\\n'));
+      return this;
     });
   }
 

src/js/parser/javascript/node.js

@@ -57,15 +57,13 @@ export default class Node {
     return this.container.transform(matrix);
   }
 
-  deferredStep() {
-    return new Promise((resolve, reject) => {
-      setTimeout(() => {
-        if (this.state.cancelRender) {
-          reject('Render cancelled');
-        } else {
-          resolve.apply(this, arguments);
-        }
-      }, 1);
+  deferredStep(value) {
+    return util.tick().then(() => {
+      if (this.state.cancelRender) {
+        throw 'Render cancelled';
+      }
+
+      return value;
     });
   }