Returning const by ref instead of const by value in PresentationSession::id

Source/modules/presentation/PresentationSession.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PresentationSession_h
 #define PresentationSession_h
 
 #include "core/events/EventTarget.h"
 #include "core/fileapi/Blob.h"
 #include "core/fileapi/FileError.h"
@@ skipping 25 matching lines @@
     static PresentationSession* take(ScriptPromiseResolver*, PassOwnPtr<WebPresentationSessionClient>);
     static PresentationSession* take(PresentationController*, PassOwnPtr<WebPresentationSessionClient>);
     ~PresentationSession() override;
 
     // EventTarget implementation.
     const AtomicString& interfaceName() const override;
     ExecutionContext* executionContext() const override;
 
     DECLARE_VIRTUAL_TRACE();
 
-    const String id() const { return m_id; }
+    const String& id() const { return m_id; }
     const WTF::AtomicString& state() const;
 
     void send(const String& message, ExceptionState&);
     void send(PassRefPtr<DOMArrayBuffer>, ExceptionState&);
     void send(PassRefPtr<DOMArrayBufferView>, ExceptionState&);
     void send(Blob*, ExceptionState&);
     void close();
 
     String binaryType() const;
     void setBinaryType(const String&);
@@ skipping 60 matching lines @@
     // For Blob data handling.
     Member<BlobLoader> m_blobLoader;
     Deque<OwnPtr<Message>> m_messages;
 
     BinaryType m_binaryType;
 };
 
 } // namespace blink
 
 #endif // PresentationSession_h