DevTools: make app banner debug messages report with different severity

third_party/WebKit/Source/devtools/protocol.json

 {
     "version": { "major": "1", "minor": "1" },
     "domains": [{
         "domain": "Inspector",
         "hidden": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications.",
@@ skipping 437 matching lines @@
             {
                 "name": "setOverlayMessage",
                 "parameters": [
                     { "name": "message", "type": "string", "optional": true, "description": "Overlay message to display when paused in debugger." }
                 ],
                 "hidden": true,
                 "description": "Sets overlay message."
             },
             {
                 "name": "requestAppBanner",
-                "returns": [
-                  { "name": "result", "type": "boolean" }
-                ],
                 "hidden": true,
                 "handlers": ["browser"]
             }
         ],
         "events": [
             {
                 "name": "domContentEventFired",
                 "parameters": [
                     { "name": "timestamp", "type": "number" }
                 ]
@@ skipping 4712 matching lines @@
                 ],
                 "returns": [
                     { "name": "accessibilityNode", "$ref": "AXNode", "description": "The <code>Accessibility.AXNode</code> for this DOM node, if it exists.", "optional": true }
                 ],
                 "description": "Fetches the accessibility node for this DOM node, if it exists.",
                 "hidden": true
             }
         ]
     }]
 }