SameSite: Teach devtools about the new 'samesite' syntax.

third_party/WebKit/LayoutTests/http/tests/inspector/resource-har-conversion-expected.txt

 CONSOLE WARNING: Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/.
 Tests conversion of Inspector's resource representation into HAR format.
 
 Page reloaded.
 {
     creator : {
         name : "WebInspector"
         version : <string>
     }
     entries : [
@@ skipping 95 matching lines @@
                         path : "/path"
                         secure : true
                         value : "y"
                     }
                     {
                         domain : undefined
                         expires : null
                         httpOnly : false
                         name : "x1"
                         path : undefined
+                        sameSite : "Strict"
                         secure : false
                         value : "y1"
                     }
                     {
                         domain : undefined
                         expires : null
                         httpOnly : false
                         name : "z2"
                         path : undefined
+                        sameSite : "Lax"
                         secure : false
                         value : "y2"
                     }
                 ]
                 headers : <object>
                 headersSize : <number>
                 httpVersion : "HTTP/1.1"
                 redirectURL : ""
                 status : 304
                 statusText : "Not Modified"
@@ skipping 92 matching lines @@
                 onContentLoad : <number>
                 onLoad : <number>
             }
             startedDateTime : <plausible>
             title : "http://127.0.0.1:8000/inspector/resource-har-conversion.html"
         }
     ]
     version : <string>
 }