Stop ignoring global leaks

The `goog.dom.ViewportSizeMonitor` (used in map.js) creates a global leak by setting `goog.UID_PROPERTY_` on the monitored window.  In order to test that we don't have other global leaks, we preemptively set the property so Mocha can compare the global before and after our tests.

test/ol.html

@@ -30,8 +30,7 @@
   <script>
     mocha.setup({
       ui: 'bdd',
-      bail: false,
-      ignoreLeaks: true
+      bail: false
     });
   </script>
   <script type="text/javascript" src="../build/proj4js/lib/proj4js-combined.js"></script>
@@ -58,6 +57,15 @@
   </script>
 
   <script type="text/javascript">
+
+    /**
+     * The goog.dom.ViewportSizeMonitor (used in map.js) creates a global leak
+     * by setting goog.UID_PROPERTY_ on the monitored window.  In order to test
+     * that we don't have other global leaks, we preemptively set the property
+     * so Mocha can compare the global before and after our tests.
+     */
+    goog.getUid(this);
+
     if (window.mochaPhantomJS) {
       mochaPhantomJS.run();
     } else {