DevTools: [Audits] Lighthouse 5.1

* This roll removes the DT-specific dark mode theme. DevTools now utilizes the dark theme provided by LH directly.
* Move from disableDeviceEmulation to emulatedFormFactor.

Bug: 772558
Change-Id: I8d000b5a2470871f977fe814eaf0202837d5062b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1623894
Commit-Queue: Connor Clark <[email protected]>
Reviewed-by: Erik Luo <[email protected]>
Reviewed-by: Paul Irish <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#664917}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: ab2bd77915e3120a8e2f33fab1c804f4d2935b92
diff --git a/front_end/externs.js b/front_end/externs.js
index 9b862d9..925c138 100644
--- a/front_end/externs.js
+++ b/front_end/externs.js
@@ -906,6 +906,24 @@
 };
 
 /**
+ * @constructor
+ * @param {!DOM} dom
+ */
+const ReportUIFeatures = function(dom) {};
+
+ReportUIFeatures.prototype = {
+  /**
+   * @param {!Document|!Element} context
+   */
+  setTemplateContext: function(context) {},
+
+  /**
+   * @param {!ReportRenderer.ReportJSON} report
+   */
+  initFeatures: function(report) {},
+};
+
+/**
  * @typedef {{
  *     rawValue: (number|boolean|undefined),
  *     id: string,