[ServiceWorker] Make Response class better conformance with the spec.

Source/bindings/core/v8/Dictionary.cpp

Index: Source/bindings/core/v8/Dictionary.cpp
diff --git a/Source/bindings/core/v8/Dictionary.cpp b/Source/bindings/core/v8/Dictionary.cpp
index da68a4e2547fb8e1b3b82ca46bfea5b725f0b56c..bcdb11df661b17d28fe53000590b0d594dcab7a9 100644
--- a/Source/bindings/core/v8/Dictionary.cpp
+++ b/Source/bindings/core/v8/Dictionary.cpp
@@ -43,7 +43,6 @@
 #include "bindings/core/v8/custom/V8ArrayBufferViewCustom.h"
 #include "bindings/core/v8/custom/V8Uint8ArrayCustom.h"
 #include "bindings/modules/v8/V8Gamepad.h"
-#include "bindings/modules/v8/V8HeaderMap.h"
 #include "bindings/modules/v8/V8Headers.h"
 #include "bindings/modules/v8/V8IDBKeyRange.h"
 #include "bindings/modules/v8/V8MIDIPort.h"
@@ -585,16 +584,6 @@ bool Dictionary::get(const String& key, Dictionary& value) const
     return true;
 }
 
-bool Dictionary::get(const String& key, RefPtr<HeaderMap>& value) const
-{
-    v8::Local<v8::Value> v8Value;
-    if (!getKey(key, v8Value))
-        return false;
-
-    value = V8HeaderMap::toNativeWithTypeCheck(m_isolate, v8Value);
-    return true;
-}
-
 bool Dictionary::get(const String& key, RefPtr<Headers>& value) const
 {
     v8::Local<v8::Value> v8Value;