Perf-Dashboard.Render sync phase sets location.hash, but the actual DOM

modifications happen asynchronously in the onhashchange() callback.

This results in nothing interesting being measured during the sync phase, and
the resulting rendering update (during the async phase) not including the
change.

Change the test to manually and synchronously trigger the onhashchange()
callback, and change the page content to detect and omit duplicate events.

Author: Matt Woodrow

resources/perf.webkit.org/public/v3/bundled-scripts.js

@@ -80,6 +80,7 @@
         function openCharts()
         {
             location.hash = '/charts/?since=1678991819934\u0026paneList=((55-1649-53731881-null-(5-2.5-500))-(55-1407-null-null-(5-2.5-500))-(55-1648-null-null-(5-2.5-500))-(55-1974-null-null-(5-2.5-500)))';
+            window.onhashchange();
         }
 
         function mockAPIs() {

resources/perf.webkit.org/public/v3/index.html

@@ -6,6 +6,7 @@ class PageRouter {
         this._currentPage = null;
         this._historyTimer = null;
         this._hash = null;
+        this._previousHash = null;
 
         window.onhashchange = this._hashDidChange.bind(this);
     }
@@ -97,8 +98,12 @@ class PageRouter {
 
     _hashDidChange()
     {
-        if (unescape(location.hash) == this._hash)
+        let unescapedHash = unescape(location.hash);
+        if (unescapedHash == this._hash)
             return;
+        if(unescapedHash == this._previousHash)
+            return;
+        this._previousHash = unescapedHash;
         this.route();
         this._hash = null;
     }