Perf - Fixes for triage page.

Handle legacy URLs for filter.
Fix step up and step down columns.

Change-Id: I920ce5d313339dd18618ecc3cd50b1f087731ca6
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/234356
Auto-Submit: Joe Gregorio <jcgregorio@google.com>
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>
diff --git a/perf/modules/triage-page-sk/triage-page-sk.js b/perf/modules/triage-page-sk/triage-page-sk.js
index 9487c50..d5523cb 100644
--- a/perf/modules/triage-page-sk/triage-page-sk.js
+++ b/perf/modules/triage-page-sk/triage-page-sk.js
@@ -130,7 +130,7 @@
   }
 
   if (ele._notBoth(colIndex)) {
-    ret.push('<td></td>');
+    ret.push(html`<td></td>`);
   }
   return ret;
 });
@@ -271,6 +271,10 @@
     dialogPolyfill.registerDialog(this.querySelector('dialog'));
     this._stateHasChanged = stateReflector(() => this._state, (state) => {
       this._state = state;
+      // For backwards compatibility with existing URLs that used 'filter'.
+      if (this._state.filter) {
+        this._state.alert_filter = this._state.filter;
+      }
       this._render();
       this._updateRange();
     });