DevTools: Clean up the Event Listeners pane data representation

Source/devtools/protocol.json

 {
     "version": { "major": "1", "minor": "1" },
     "domains": [{
         "domain": "Inspector",
         "hidden": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications."
@@ skipping 2148 matching lines @@
             },
             {
                 "id": "EventListener",
                 "type": "object",
                 "hidden": true,
                 "properties": [
                     { "name": "type", "type": "string", "description": "<code>EventListener</code>'s type." },
                     { "name": "useCapture", "type": "boolean", "description": "<code>EventListener</code>'s useCapture." },
                     { "name": "isAttribute", "type": "boolean", "description": "<code>EventListener</code>'s isAttribute." },
                     { "name": "nodeId", "$ref": "NodeId", "description": "Target <code>DOMNode</code> id." },
-                    { "name": "handlerBody", "type": "string", "description": "Event handler function body." },
                     { "name": "location", "$ref": "Debugger.Location", "description": "Handler code location." },
-                    { "name": "sourceName", "type": "string", "optional": true, "description": "Source script URL." },
                     { "name": "handler", "$ref": "Runtime.RemoteObject", "optional": true, "description": "Event handler function value." }
                 ],
                 "description": "DOM interaction is implemented in terms of mirror objects that represent the actual DOM nodes. DOMNode is a base node mirror type."
             },
             {
                 "id": "RGBA",
                 "type": "object",
                 "properties": [
                     { "name": "r", "type": "integer", "description": "The red component, in the [0-255] range." },
                     { "name": "g", "type": "integer", "description": "The green component, in the [0-255] range." },
@@ skipping 2625 matching lines @@
             {
                 "name": "animationPlayerCreated",
                 "parameters": [
                     { "name": "player", "$ref": "AnimationPlayer", "description": "AnimationPlayer that was created." }
                 ],
                 "hidden": true
             }
         ]
     }]
 }