Web Inspector: Improve speed of Linkifier.reset operation.
https://bugs.webkit.org/show_bug.cgi?id=110696

Reviewed by Yury Semikhatsky.

Linkifier calls Location.dispose N times and each dispose method calls Array.remove
which scans entire array and does splice. So the complexity of Linkifier.reset
is O(N^2). I replaced the arrays with Set and got O(N) complexity.

Drive by fix: The identifier generator was slightly changed.
Now it produces identifiers that couldn't be converted into a number.
So the engine will never convert Set/Map object into an array.

Source/WebCore:

* inspector/front-end/Script.js:
(WebInspector.Script):
(WebInspector.Script.prototype.updateLocations):
(WebInspector.Script.prototype.createLiveLocation):
* inspector/front-end/UISourceCode.js:
(WebInspector.UISourceCode):
(WebInspector.UISourceCode.prototype.addLiveLocation):
(WebInspector.UISourceCode.prototype.updateLiveLocations):
* inspector/front-end/utilities.js:

LayoutTests:

* inspector/debugger/callstack-placards-discarded.html:
* inspector/debugger/linkifier.html:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@143889 268f45cc-cd09-0410-ab3c-d52691b4dbfc