DevTools: remove unused UI related code

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

Index: third_party/WebKit/Source/devtools/front_end/ui/ContextMenu.js
diff --git a/third_party/WebKit/Source/devtools/front_end/ui/ContextMenu.js b/third_party/WebKit/Source/devtools/front_end/ui/ContextMenu.js
index 4eed4c0d5d3bb173e18d7a040271a5d6e774a522..1be132b683929cb1619dba866ab39e033a7256bd 100644
--- a/third_party/WebKit/Source/devtools/front_end/ui/ContextMenu.js
+++ b/third_party/WebKit/Source/devtools/front_end/ui/ContextMenu.js
@@ -387,8 +387,6 @@ UI.ContextMenu = class extends UI.ContextSubMenuItem {
     }
 
     var menuObject = this._buildDescriptors();
-
-    UI._contextMenu = this;

[luoe, 2017/05/22 17:50:47]

Added:
https://chromium.googlesource.com/chromium/src/+/5189f94c96828d4422412f19411f...
Used to have a reference to the last shown ContextMenu so that
contextmenuitemselected calls from the Host
would route to the correct context menu.

Now, contextmenus listen for Host events themselves.

     if (this._useSoftMenu || UI.ContextMenu._useSoftMenu || InspectorFrontendHost.isHostedMode()) {
       this._softMenu = new UI.SoftContextMenu(menuObject, this._itemSelected.bind(this));
       this._softMenu.show(this._event.target.ownerDocument, new AnchorBox(this._x, this._y, 0, 0));