fix(Headers): serializable toJSON

fixes #6073

Closes #6714

modules/angular2/src/http/headers.ts

@@ -9,6 +9,7 @@ import {
 import {BaseException, WrappedException} from 'angular2/src/facade/exceptions';
 import {
   isListLikeIterable,
+  iterateListLike,
   Map,
   MapWrapper,
   StringMapWrapper,
@@ -131,7 +132,17 @@ export class Headers {
   /**
    * Returns string of all headers.
    */
-  toJSON(): string { return Json.stringify(this.values()); }
+  toJSON(): {[key: string]: any} {
+    let serializableHeaders = {};
+    this._headersMap.forEach((values: string[], name: string) => {
+      let list = [];
+
+      iterateListLike(values, val => list = ListWrapper.concat(list, val.split(',')));
+
+      serializableHeaders[name] = list;
+    });
+    return serializableHeaders;
+  }
 
   /**
    * Returns list of header values for a given name.

modules/angular2/test/http/headers_spec.ts

@@ -1,4 +1,5 @@
 import {Headers} from 'angular2/src/http/headers';
+import {Json} from 'angular2/src/facade/lang';
 import {Map, StringMapWrapper} from 'angular2/src/facade/collection';
 import {
   AsyncTestCompleter,
@@ -62,6 +63,42 @@ export function main() {
         expect(/bar, ?baz/g.test(headers.getAll('foo')[0])).toBe(true);
       });
     });
+
+
+    describe('.toJSON()', () => {
+      let headers = null;
+      let inputArr = null;
+      let obj = null;
+
+      beforeEach(() => {
+        headers = new Headers();
+        inputArr = ['application/jeisen', 'application/jason', 'application/patrickjs'];
+        obj = {'Accept': inputArr};
+        headers.set('Accept', inputArr);
+      });
+
+
+      it('should be serializable with toJSON', () => {
+        let stringifed = Json.stringify(obj);
+        let serializedHeaders = Json.stringify(headers);
+        expect(serializedHeaders).toEqual(stringifed);
+      });
+
+
+      it('should be able to parse serialized header', () => {
+        let stringifed = Json.stringify(obj);
+        let serializedHeaders = Json.stringify(headers);
+        expect(Json.parse(serializedHeaders)).toEqual(Json.parse(stringifed));
+      });
+
+
+      it('should be able to recreate serializedHeaders', () => {
+        let serializedHeaders = Json.stringify(headers);
+        let parsedHeaders = Json.parse(serializedHeaders);
+        let recreatedHeaders = new Headers(parsedHeaders);
+        expect(Json.stringify(parsedHeaders)).toEqual(Json.stringify(recreatedHeaders));
+      });
+    });
   });
 
   describe('.fromResponseHeaderString()', () => {