Fixes a bug where touch device scripts were not cleared on exit of device mode in devtools.

Source/devtools/front_end/emulation/OverridesSupport.js

 /*
  * Copyright (C) 2012 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 687 matching lines @@
          */
         const injectedFunction = function() {
             const touchEvents = ["ontouchstart", "ontouchend", "ontouchmove", "ontouchcancel"];
             var recepients = [window.__proto__, document.__proto__];
             for (var i = 0; i < touchEvents.length; ++i) {
                 for (var j = 0; j < recepients.length; ++j) {
                     if (!(touchEvents[i] in recepients[j]))
                         Object.defineProperty(recepients[j], touchEvents[i], { value: null, writable: true, configurable: true, enumerable: true });
                 }
             }
-        }
+        };
 
         var symbol = WebInspector.OverridesSupport._touchEventsScriptIdSymbol;
 
-        if (emulationEnabled && target[symbol] !== -1) {
-            target[symbol] = -1;
+        if (typeof target[symbol] !== "undefined") {
+            target.pageAgent().removeScriptToEvaluateOnLoad(target[symbol]);
+            delete target[symbol];
+        }
+
+        if (emulationEnabled)
             target.pageAgent().addScriptToEvaluateOnLoad("(" + injectedFunction.toString() + ")()", scriptAddedCallback);
-        } else {
-            if (typeof target[symbol] !== "undefined") {
-                target.pageAgent().removeScriptToEvaluateOnLoad(target[symbol]);
-                delete target[symbol];
-            }
-        }
 
         /**
          * @param {?Protocol.Error} error
          * @param {string} scriptId
          */
         function scriptAddedCallback(error, scriptId)
         {
             if (error)
                 delete target[symbol];
             else
@@ skipping 87 matching lines @@
     },
 
     __proto__: WebInspector.Object.prototype
 }
 
 
 /**
  * @type {!WebInspector.OverridesSupport}
  */
 WebInspector.overridesSupport;