Fix reference to Runtime in UIDevtoolsUtils

This issue went unnoticed because of two different CLs touching the same
kind of code in unrelated parts of DevTools. It is likely that no tests
covered this codepath, blocking one of the CLs from being submitted.

Bug: chromium:1006759
Tbr: yangguo@chromium.org
Change-Id: If3ef1d86e3ab1d887ece3372649705c96e0b0ce6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1834144Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Tim Van der Lippe <tvanderlippe@chromium.org>
Auto-Submit: Tim Van der Lippe <tvanderlippe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702003}

third_party/blink/renderer/devtools/front_end/timeline/UIDevtoolsUtils.js

@@ -36,7 +36,7 @@ Timeline.UIDevtoolsUtils = class {
    * @return {boolean}
    */
   static isUiDevTools() {
-    return Runtime.queryParam('uiDevTools') === 'true';
+    return Root.Runtime.queryParam('uiDevTools') === 'true';
   }
 
   /**