DevTools: [Audits] Enable report features.

Change-Id: I68f882e5e906b66f23808067b1039dc8789accc8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1651062
Commit-Queue: Connor Clark <[email protected]>
Reviewed-by: Paul Irish <[email protected]>
Reviewed-by: Erik Luo <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#672245}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 05ecc20fecdd57fcb7f1a8c6c7b72713e6011ddf
diff --git a/front_end/externs.js b/front_end/externs.js
index ace7420..0d8299b 100644
--- a/front_end/externs.js
+++ b/front_end/externs.js
@@ -909,7 +909,13 @@
  * @constructor
  * @param {!DOM} dom
  */
-const ReportUIFeatures = function(dom) {};
+const ReportUIFeatures = function(dom) {
+  /** @type {!ReportRenderer.ReportJSON} */
+  this.json;
+
+  /** @type {!Document} */
+  this._document;
+};
 
 ReportUIFeatures.prototype = {
   /**
@@ -921,6 +927,8 @@
    * @param {!ReportRenderer.ReportJSON} report
    */
   initFeatures: function(report) {},
+
+  _resetUIState: function() {},
 };
 
 /**