DevTools: brush up audits 2 launcher UI, allow multiple audit runs, introduce landing page.

third_party/WebKit/Source/devtools/front_end/audits2/audits2Tree.css

+/*
+ * Copyright 2017 The Chromium Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+.tree-outline .audits2-report-tree-item {
+  min-height: 36px;
+  padding: 2px 3px;
+  line-height: 16px;
+}
+
+.tree-outline li {
+  min-height: 25px;
+}
+
+.audits2-tree-subtitle-pass,
+.audits2-tree-subtitle-average,
+.audits2-tree-subtitle-fail {
+  flex: auto;
+  text-align: end;
+  margin-right: 10px;
+  font-size: inherit;
+  background: inherit;
+}
+
+.audits2-tree-subtitle-pass {
+  color: var(--pass-color);
+}
+
+.audits2-tree-subtitle-average {
+  color: var(--average-color);
+}
+
+.audits2-tree-subtitle-fail {
+  color: var(--fail-color);
+}