[DevTools] Add interstitial events to Inspector domain.

Source/devtools/protocol.json

 {
     "version": { "major": "1", "minor": "1" },
     "domains": [{
         "domain": "Inspector",
         "hidden": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications."
@@ skipping 27 matching lines @@
                 "description": "Fired when remote debugging connection is about to be terminated. Contains detach reason.",
                 "parameters": [
                     { "name": "reason", "type": "string", "description": "The reason why connection has been terminated." }
                 ],
                 "handlers": ["browser"]
             },
             {
                 "name": "targetCrashed",
                 "description": "Fired when debugging target has crashed",
                 "handlers": ["browser"]
+            },
+            {
+                "name": "interstitialShown",
+                "description": "Fired when interstitial page was shown",
+                "handlers": ["browser"]
+            },
+            {
+                "name": "interstitialHidden",
+                "description": "Fired when interstitial page was hidden",
+                "handlers": ["browser"]
             }
         ]
     },
     {
         "domain": "Memory",
         "hidden": true,
         "commands": [
             {
                 "name": "getDOMCounters",
                 "returns": [
@@ skipping 4256 matching lines @@
             {
                 "name": "dataAvailable",
                 "parameters": [
                     {"name": "value", "type": "array", "items": { "$ref": "PowerEvent" }, "description": "List of power events." }
                 ],
                 "handlers": ["browser", "frontend"]
             }
         ]
     }]
 }