DevTools: [CSS] introduce strong types

Source/devtools/protocol.json

 {
     "version": { "major": "1", "minor": "1" },
     "domains": [{
         "domain": "Inspector",
         "hidden": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications.",
@@ skipping 2968 matching lines @@
                     { "name": "computedStyle", "type": "array", "items": { "$ref": "CSSComputedStyleProperty" }, "description": "Computed style for the specified DOM node." }
                 ],
                 "description": "Returns the computed style for a DOM node identified by <code>nodeId</code>."
             },
             {
                 "name": "getPlatformFontsForNode",
                 "parameters": [
                     { "name": "nodeId", "$ref": "DOM.NodeId" }
                 ],
                 "returns": [
-                    { "name": "cssFamilyName", "type": "string", "description": "Font family name which is determined by computed style." },
                     { "name": "fonts", "type": "array", "items": { "$ref": "PlatformFontUsage" }, "description": "Usage statistics for every employed platform font." }
                 ],
                 "description": "Requests information about platform fonts which we used to render child TextNodes in the given node.",
                 "hidden": true
             },
             {
                 "name": "getStyleSheetText",
                 "parameters": [
                     { "name": "styleSheetId", "$ref": "StyleSheetId" }
                 ],
@@ skipping 2047 matching lines @@
                 "description": "The security state of the page changed.",
                 "parameters": [
                     { "name": "securityState", "$ref": "SecurityState", "description": "Security state." },
                     { "name": "explanations", "type": "array", "items": { "$ref": "SecurityStateExplanation" }, "description": "List of explanations for the security state. If the overall security state is `insecure` or `warning`, at least one corresponding explanation should be included.", "optional": true }
                 ],
                 "handlers": ["browser"]
             }
         ]
     }]
 }