[Fetch API] Put body members directly on Response/Request

LayoutTests/http/tests/serviceworker/resources/fetch-body-mixin-worker.js

 self.onmessage = function(e) {
     var message = e.data;
     if ('port' in message) {
         port = message.port;
         doTextTest(port);
     }
 };
 
 function quit(port) {
     port.postMessage('quit');
 }
 
 function doFetchTwiceTest(port) {
   var p1Out = p2Out = null;
 
   fetch('doctype.html')
   .then(function(response) {
-      var p1 = response.body.asText();
-      var p2 = response.body.asText();
+      var p1 = response.text();
+      var p2 = response.text();
 
       p1.then(function(obj) {
           p1Out = obj;
           if (p2Out) {
               complete();
           }
       });
       p2.catch(function(e) {
           p2Out = e;
           if (p1Out) {
               complete();
           }
       });
   });
 
   function complete() {
       port.postMessage(p1Out + ' : ' + p2Out.name);
       quit(port);
   }
 }
 
 function doArrayBufferTest(port) {
     fetch('doctype.html')
     .then(function(response) {
-        response.body.asArrayBuffer()
+        response.arrayBuffer()
         .then(function(b) {
             port.postMessage('ArrayBuffer: ' + b.byteLength);
             doFetchTwiceTest(port);
         });
     });
 }
 
 function doBlobTest(port) {
     fetch('doctype.html')
     .then(function(response) {
-        response.body.asBlob()
+        response.blob()
         .then(function(blob) {
             port.postMessage('Blob: ' + blob.size + " : " + blob.type);
             doArrayBufferTest(port);
         });
     });
 }
 
 function doJSONFailedTest(port) {
   fetch('doctype.html')
   .then(function(response) {
-      response.body.asJSON()
+      response.json()
       .catch(function(e) {
           port.postMessage('JSON: ' + e.name);
           doBlobTest(port);
       });
   });
 }
 
 function doJSONTest(port) {
     fetch('simple.json')
     .then(function(response) {
-        response.body.asJSON()
+        response.json()
         .then(function(json) {
             port.postMessage('JSON: ' + json['a'] + ' ' + json['b']);
             doJSONFailedTest(port);
         });
     });
 }
 
 function doTextTest(port) {
   fetch('doctype.html')
   .then(function(response) {
-      response.body.asText()
+      response.text()
       .then(function(txt) {
           port.postMessage('Text: ' + txt);
           doJSONTest(port);
       });
   });
 }