DevTools: Remove unused variables. Disallow unused variables with eslint

third_party/WebKit/Source/devtools/front_end/sources/JavaScriptSourceFrame.js

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 393 matching lines @@
     var leftCorner = this.textEditor.cursorPositionToCoordinates(lineNumber, token.startColumn);
     var rightCorner = this.textEditor.cursorPositionToCoordinates(lineNumber, token.endColumn - 1);
     var anchorBox = new AnchorBox(leftCorner.x, leftCorner.y, rightCorner.x - leftCorner.x, leftCorner.height);
 
     anchorBox.highlight = {lineNumber: lineNumber, startColumn: token.startColumn, endColumn: token.endColumn - 1};
 
     return anchorBox;
   }
 
   _resolveObjectForPopover(anchorBox, showCallback, objectGroupName) {
-    var target = UI.context.flavor(SDK.Target);
     var selectedCallFrame = UI.context.flavor(SDK.DebuggerModel.CallFrame);
     if (!selectedCallFrame) {
       this._popoverHelper.hidePopover();
       return;
     }
     var lineNumber = anchorBox.highlight.lineNumber;
     var startHighlight = anchorBox.highlight.startColumn;
     var endHighlight = anchorBox.highlight.endColumn;
     var line = this.textEditor.line(lineNumber);
     if (!anchorBox.forSelection) {
@@ skipping 947 matching lines @@
   hide() {
     if (!this.bookmark)
       return;
     this.bookmark.clear();
     this.bookmark = null;
   }
 };
 
 Sources.JavaScriptSourceFrame.BreakpointDecoration.bookmarkSymbol = Symbol('bookmark');
 Sources.JavaScriptSourceFrame.BreakpointDecoration._elementSymbolForTest = Symbol('element');