Make sure getAttribute() / setAttribute() callers use AtomicStrings

Source/core/html/HTMLSourceElement.h

Index: Source/core/html/HTMLSourceElement.h
diff --git a/Source/core/html/HTMLSourceElement.h b/Source/core/html/HTMLSourceElement.h
index 21f9777ff7586ee7861b62418981d41450ad8e95..0002d21070621730e04f0f46c74f8b8a5bf68b54 100644
--- a/Source/core/html/HTMLSourceElement.h
+++ b/Source/core/html/HTMLSourceElement.h
@@ -35,11 +35,11 @@ class HTMLSourceElement FINAL : public HTMLElement {
 public:
     static PassRefPtr<HTMLSourceElement> create(Document&);
 
-    String media() const;
-    String type() const;
+    const AtomicString& media() const;
+    const AtomicString& type() const;
     void setSrc(const String&);
-    void setMedia(const String&);
-    void setType(const String&);
+    void setMedia(const AtomicString&);
+    void setType(const AtomicString&);
 
     void scheduleErrorEvent();
     void cancelPendingErrorEvent();