DevTools: implement enable/disable commands in DOMAgent

Source/devtools/protocol.json

 {
     "version": { "major": "1", "minor": "1" },
     "domains": [{
         "domain": "Inspector",
         "hidden": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications."
@@ skipping 1954 matching lines @@
                     { "name": "paddingColor", "$ref": "RGBA", "optional": true, "description": "The padding highlight fill color (default: transparent)." },
                     { "name": "borderColor", "$ref": "RGBA", "optional": true, "description": "The border highlight fill color (default: transparent)." },
                     { "name": "marginColor", "$ref": "RGBA", "optional": true, "description": "The margin highlight fill color (default: transparent)." },
                     { "name": "eventTargetColor", "$ref": "RGBA", "optional": true, "hidden": true, "description": "The event target element highlight fill color (default: transparent)." }
                 ],
                 "description": "Configuration data for the highlighting of page elements."
             }
         ],
         "commands": [
             {
+                "name": "enable",
+                "description": "Enables DOM agent for the given page."
+            },
+            {
+                "name": "disable",
+                "description": "Disables DOM agent for the given page."
+            },
+            {
                 "name": "getDocument",
                 "returns": [
                     { "name": "root", "$ref": "Node", "description": "Resulting node." }
                 ],
                 "description": "Returns the root DOM node to the caller."
             },
             {
                 "name": "requestChildNodes",
                 "parameters": [
                     { "name": "nodeId", "$ref": "NodeId", "description": "Id of the node to get children for." },
@@ skipping 2152 matching lines @@
             {
                 "name": "dataAvailable",
                 "parameters": [
                     {"name": "value", "type": "array", "items": { "$ref": "PowerEvent" }, "description": "List of power events." }
                 ],
                 "handlers": ["browser", "frontend"]
             }
         ]
     }]
 }