DevTools: [MediaQueryInspector] Compute media query length on backend

Source/devtools/protocol.json

 {
     "version": { "major": "1", "minor": "1" },
     "domains": [{
         "domain": "Inspector",
         "hidden": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications."
@@ skipping 2594 matching lines @@
                 "items": { "$ref": "MediaQueryExpression" },
                 "description": "An array of media query expressions.",
                 "hidden": true
             },
             {
                 "id": "MediaQueryExpression",
                 "type": "object",
                 "properties": [
                     { "name": "value", "type": "number", "description": "Media query expression value."},
                     { "name": "unit", "type": "string", "description": "Media query expression units."},
-                    { "name": "feature", "type": "string", "description": "Media query expression feature."}
+                    { "name": "feature", "type": "string", "description": "Media query expression feature."},
+                    { "name": "computedLength", "type": "number", "optional": true, "description": "Computed length of media query expression (if applicable)."}
                 ],
                 "description": "Media query expression data.",
                 "hidden": true
             },
             {
                 "id": "PlatformFontUsage",
                 "type": "object",
                 "properties": [
                     { "name": "familyName", "type": "string", "description": "Font's family name reported by platform."},
                     { "name": "glyphCount", "type": "number", "description": "Amount of glyphs that were rendered with this font."}
@@ skipping 1566 matching lines @@
             {
                 "name": "dataAvailable",
                 "parameters": [
                     {"name": "value", "type": "array", "items": { "$ref": "PowerEvent" }, "description": "List of power events." }
                 ],
                 "handlers": ["browser", "frontend"]
             }
         ]
     }]
 }