Get the url from the result array in GeckoProfiler.stop

Previously for gecko profiler commands we were getting the test url by
running a script that returns `document.documentURI`. This was working
fine for most cases. But when one of our tests actually navigates to a
different page from the starting page, it gets the destination url
instead of the initial url. Since we need the initial url, it's better
not to get the url like this, and get it directly from the `result`
array.

Note that chrome trace command does something similar [here](https://github.com/sitespeedio/browsertime/blob/e3e5a46f6c9070c0ab66e543b85e60d021edc848/lib/core/engine/command/chromeTrace.js#L42).

lib/core/engine/command/geckoProfiler.js

@@ -1,11 +1,12 @@
 import intel from 'intel';
 const log = intel.getLogger('browsertime.command.geckoprofiler');
 export class GeckoProfiler {
-  constructor(GeckoProfiler, browser, index, options) {
+  constructor(GeckoProfiler, browser, index, options, result) {
     this.GeckoProfiler = GeckoProfiler;
     this.browser = browser;
     this.index = index;
     this.options = options;
+    this.result = result;
   }
 
   async start() {
@@ -25,11 +26,7 @@ export class GeckoProfiler {
   async stop() {
     if (this.options.browser === 'firefox') {
       if (this.options.firefox.geckoProfilerRecordingType === 'custom') {
-        const url = await this.browser
-          .getDriver()
-          .executeScript('return document.documentURI;');
-
-        return this.GeckoProfiler.stop(this.index, url);
+        return this.GeckoProfiler.stop(this.index, this.result[0].url);
       }
     } else {
       throw new Error('Geckoprofiler only works in Firefox');

lib/core/engine/iteration.js

@@ -159,7 +159,8 @@ export class Iteration {
         browserProfiler,
         browser,
         index,
-        this.options
+        this.options,
+        result
       );
       const cdp = new ChromeDevelopmentToolsProtocol(
         engineDelegate,