Put URL = URL || webkitURL in compatibility.js

Declares the URL variable globally. If the feature is not
supported, the variable will still be declared, but have the
"undefined" value.

Supported by:

- Firefox 4
  Firefox 21 in Web worker

- Chrome 8  (prefixed as webkitURL), 23+ unprefixed
  Chrome 10 (prefixed as webkitURL) in Web Worker, 23+ unprefixed

- Opera 15
  Opera 15 in Web Worker

- Internet Explorer 10
  Internet Explorer 11 in Web Worker

- Safari 6 (prefixed as webkitURL)
  Safari 6 (prefixed as webkitURL) in Web Worker

web/compatibility.js

@@ -92,6 +92,13 @@ if (typeof PDFJS === 'undefined') {
   window.Float64Array = TypedArray;
 })();
 
+// URL = URL || webkitURL
+(function normalizeURLObject() {
+  if (!window.URL && window.webkitURL) {
+    window.URL = window.webkitURL;
+  }
+})();
+
 // Object.create() ?
 (function checkObjectCreateCompatibility() {
   if (typeof Object.create !== 'undefined')

web/viewer.js

@@ -14,6 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+/* globals URL*/
 /* globals PDFJS, PDFBug, FirefoxCom, Stats, Cache, PDFFindBar */
 /* globals PDFFindController, ProgressBar, getFileName, CustomStyle */
 /* globals getOutputScale, TextLayerBuilder */
@@ -975,8 +976,7 @@ var PDFView = {
 //      );
 //  }
 //#endif
-    var URL = window.URL || window.webkitURL;
-    // If the PDF is not ready yet, or if createObjectURL is not supported,
+    // If the PDF is not ready yet, or if URL.createObjectURL is not supported,
     // just try to download with the url.
     if (!this.pdfDocument || !URL) {
         noData();