[ServiceWorker] Implement Headers class.

Source/modules/serviceworkers/HeadersForEachCallback.idl

Index: Source/modules/serviceworkers/HeadersForEachCallback.idl
diff --git a/Source/modules/serviceworkers/HeaderMapForEachCallback.idl b/Source/modules/serviceworkers/HeadersForEachCallback.idl
similarity index 51%
copy from Source/modules/serviceworkers/HeaderMapForEachCallback.idl
copy to Source/modules/serviceworkers/HeadersForEachCallback.idl
index d6bbb8dfc96e0e4a3c1753d2b6bf38e427baea15..d61e83af562b586e183af1080d30f9e12c69bb7e 100644
--- a/Source/modules/serviceworkers/HeaderMapForEachCallback.idl
+++ b/Source/modules/serviceworkers/HeadersForEachCallback.idl
@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-callback interface HeaderMapForEachCallback {
-    [CallWith=ThisValue] boolean handleItem(DOMString value, DOMString key, HeaderMap map);
-    boolean handleItem(DOMString value, DOMString key, HeaderMap map);
+// This IDL is not spec'd yet.
+// http://fetch.spec.whatwg.org/#headers-class
+callback interface HeadersForEachCallback {
+    [CallWith=ThisValue] boolean handleItem(DOMString value, DOMString key, Headers map);
+    boolean handleItem(DOMString value, DOMString key, Headers map);
 };