move (create|revoke)ObjectURL & createBlob to helpers

- so that when we can fallback to window.webkitURL if
  window.URL isn't defined

Author: etpinard

src/snapshot/filesaver.js

@@ -9,6 +9,7 @@
 'use strict';
 
 var Lib = require('../lib');
+var helpers = require('./helpers');
 
 /*
 * substantial portions of this code from FileSaver.js
@@ -45,23 +46,23 @@ function fileSaver(url, name, format) {
         if(Lib.isIE()) {
             // At this point we are only dealing with a decoded SVG as
             // a data URL (since IE only supports SVG)
-            blob = createBlob(url, format);
+            blob = helpers.createBlob(url, 'svg');
             window.navigator.msSaveBlob(blob, name);
             blob = null;
             return resolve(name);
         }
 
         if(canUseSaveLink) {
-            blob = createBlob(url, format);
-            objectUrl = window.URL.createObjectURL(blob);
+            blob = helpers.createBlob(url, format);
+            objectUrl = helpers.createObjectURL(blob);
 
             saveLink.href = objectUrl;
             saveLink.download = name;
             document.body.appendChild(saveLink);
             saveLink.click();
 
             document.body.removeChild(saveLink);
-            window.URL.revokeObjectURL(objectUrl);
+            helpers.revokeObjectURL(objectUrl);
             blob = null;
 
             return resolve(name);
@@ -81,24 +82,4 @@ function isIE9orBelow() {
     );
 }
 
-// Taken from https://bl.ocks.org/nolanlawson/0eac306e4dac2114c752
-function fixBinary(b) {
-    var len = b.length;
-    var buf = new ArrayBuffer(len);
-    var arr = new Uint8Array(buf);
-    for(var i = 0; i < len; i++) {
-        arr[i] = b.charCodeAt(i);
-    }
-    return buf;
-}
-
-function createBlob(url, format) {
-    if(format === 'svg') {
-        return new window.Blob([url]);
-    } else {
-        var binary = fixBinary(window.atob(url));
-        return new window.Blob([binary], {type: 'image/' + format});
-    }
-}
-
 module.exports = fileSaver;

src/snapshot/helpers.js

@@ -36,6 +36,36 @@ exports.encodeSVG = function(svg) {
     return 'data:image/svg+xml,' + encodeURIComponent(svg);
 };
 
+var DOM_URL = window.URL || window.webkitURL;
+
+exports.createObjectURL = function(blob) {
+    return DOM_URL.createObjectURL(blob);
+};
+
+exports.revokeObjectURL = function(url) {
+    return DOM_URL.revokeObjectURL(url);
+};
+
+exports.createBlob = function(url, format) {
+    if(format === 'svg') {
+        return new window.Blob([url], {type: 'image/svg+xml;charset=utf-8'});
+    } else {
+        var binary = fixBinary(window.atob(url));
+        return new window.Blob([binary], {type: 'image/' + format});
+    }
+};
+
+// Taken from https://bl.ocks.org/nolanlawson/0eac306e4dac2114c752
+function fixBinary(b) {
+    var len = b.length;
+    var buf = new ArrayBuffer(len);
+    var arr = new Uint8Array(buf);
+    for(var i = 0; i < len; i++) {
+        arr[i] = b.charCodeAt(i);
+    }
+    return buf;
+}
+
 exports.IMAGE_URL_PREFIX = /^data:image\/\w+;base64,/;
 
 exports.MSG_IE_BAD_FORMAT = 'Sorry IE does not support downloading from canvas. Try {format:\'svg\'} instead.';