Web Inspector: Content should not be lost when uiSourceCode's file was removed externally on file system.
https://bugs.webkit.org/show_bug.cgi?id=113581

Reviewed by Pavel Feldman.

* inspector/front-end/IsolatedFileSystem.js:
(WebInspector.IsolatedFileSystem.prototype.errorHandler):
(WebInspector.IsolatedFileSystem.prototype.requestFileContent):
(WebInspector.IsolatedFileSystem.prototype.fileSystemLoaded):
* inspector/front-end/UISourceCode.js:
(WebInspector.UISourceCode.prototype.checkContentUpdated.contentLoaded):
(WebInspector.UISourceCode.prototype.checkContentUpdated):
(WebInspector.UISourceCode.prototype._commitContent):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147227 268f45cc-cd09-0410-ab3c-d52691b4dbfc