[DevTools] Introduce a sidebar with a drop-down

third_party/WebKit/Source/devtools/front_end/quick_open/filteredListWidget.css

 /*
  * Copyright (c) 2015 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.
  */
 
 .filtered-list-widget {
     display: flex;
     flex-direction: column;
     flex: auto;
 }
 
 .filtered-list-widget-prompt-element {
     flex: 0 0 34px;
     border: 0;
     margin: 0;
     padding: 0 6px;
     z-index: 1;
     font-size: inherit;
 }
 
+.filtered-list-widget-input-container {
+    display: flex;
+    flex-direction: row;
+    align-items: center;
+    margin: 11px 0 4px 0;
+    height: 18px;
+    flex-shrink: 0;
+}
+
 .filtered-list-widget-input {
     white-space: pre;
-    height: 18px;
-    margin-top: 12px;
     overflow: hidden;
     flex: auto;
+    align-self: stretch;
+    margin-top: 1px;
+}
+
+.filtered-list-input-icon {
+    flex-shrink: 1;
+    margin-left: 8px;
 }
 
 .filtered-list-widget-progress {
     flex: none;
     background: rgba(0, 0, 0, 0.2);
     height: 2px;
 }
 
 .filtered-list-widget-progress-bar {
     background-color: #2196F3;
@@ skipping 74 matching lines @@
 }
 
 .not-found-text {
     height: 34px;
     line-height: 34px;
     padding-left: 4px;
     font-style: italic;
     color: #888;
     background: #fbfbfb;
 }
+
+.hovered {
+    background-color: #F7F7F7;
+}