DevTools: protocol: add "canEmulateNetworkConditions" method definition.

Source/devtools/protocol.json

 {
     "version": { "major": "1", "minor": "1" },
     "domains": [{
         "domain": "Inspector",
         "hidden": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications."
@@ skipping 1191 matching lines @@
                 "returns": [
                     { "name": "result", "type": "boolean", "description": "True if browser cookies can be cleared." }
                 ]
             },
             {
                 "name": "clearBrowserCookies",
                 "description": "Clears browser cookies.",
                 "handlers": ["browser"]
             },
             {
+                "name": "canEmulateNetworkConditions",
+                "description": "Tells whether emulation of network conditions is supported.",
+                "returns": [
+                  { "name": "result", "type": "boolean", "description": "True if emulation of network conditions is supported." }
+                ],
+                "hidden": true,
+                "handlers": ["browser"]
+            },
+            {
                 "name": "emulateNetworkConditions",
                 "description": "Activates emulation of network conditions.",
                 "parameters": [
                     { "name": "offline", "type": "boolean", "description": "True to emulate internet disconnection." },
                     { "name": "latency", "type": "number", "description": "Additional latency (ms)." },
                     { "name": "downloadThroughput", "type": "number", "description": "Maximal aggregated download throughput." },
                     { "name": "uploadThroughput", "type": "number", "description": "Maximal aggregated upload throughput." }
                 ],
                 "hidden": true,
                 "handlers": ["browser", "renderer"]
@@ skipping 3063 matching lines @@
             {
                 "name": "dataAvailable",
                 "parameters": [
                     {"name": "value", "type": "array", "items": { "$ref": "PowerEvent" }, "description": "List of power events." }
                 ],
                 "handlers": ["browser", "frontend"]
             }
         ]
     }]
 }