Update HTTPHeaderMap wrappers to use AtomicString type for header values

Source/core/inspector/InspectorResourceAgent.h

Index: Source/core/inspector/InspectorResourceAgent.h
diff --git a/Source/core/inspector/InspectorResourceAgent.h b/Source/core/inspector/InspectorResourceAgent.h
index 6968882c9574f99e2aad6209dd6173bcf0d409a7..220cb1483caa786929ada04806a9590ce9908502 100644
--- a/Source/core/inspector/InspectorResourceAgent.h
+++ b/Source/core/inspector/InspectorResourceAgent.h
@@ -101,7 +101,7 @@ public:
     void didReceiveScriptResponse(unsigned long identifier);
 
     void documentThreadableLoaderStartedLoadingForClient(unsigned long identifier, ThreadableLoaderClient*);
-    void willLoadXHR(XMLHttpRequest*, ThreadableLoaderClient*, const String& method, const KURL&, bool async, PassRefPtr<FormData> body, const HTTPHeaderMap& headers, bool includeCrendentials);
+    void willLoadXHR(XMLHttpRequest*, ThreadableLoaderClient*, const AtomicString& method, const KURL&, bool async, PassRefPtr<FormData> body, const HTTPHeaderMap& headers, bool includeCrendentials);
     void didFailXHRLoading(XMLHttpRequest*, ThreadableLoaderClient*);
     void didFinishXHRLoading(XMLHttpRequest*, ThreadableLoaderClient*, unsigned long identifier, ScriptString sourceString, const String&, const String&, unsigned);
     void didReceiveXHRResponse(unsigned long identifier);