[DevTools] Introduce a sidebar with a drop-down

third_party/WebKit/Source/devtools/front_end/ui/ListControl.js

Index: third_party/WebKit/Source/devtools/front_end/ui/ListControl.js
diff --git a/third_party/WebKit/Source/devtools/front_end/ui/ListControl.js b/third_party/WebKit/Source/devtools/front_end/ui/ListControl.js
index b55c2034cdfbfaaa3619d0e399d2c49445532b4f..0432efca80723207e71ff36f46bac0a91a85fe0a 100644
--- a/third_party/WebKit/Source/devtools/front_end/ui/ListControl.js
+++ b/third_party/WebKit/Source/devtools/front_end/ui/ListControl.js
@@ -224,6 +224,14 @@ UI.ListControl = class {
   }
 
   /**
+   * @param {!T} item
+   * @return {?Element}
+   */
+  elementForItem(item) {
+    return this._itemToElement.get(item);
+  }
+
+  /**
    * @param {T} item
    * @param {boolean=} center
    */