Move EmptyString, kWhitespace and the BOM to base.

chrome_frame/chrome_active_document.cc

Index: chrome_frame/chrome_active_document.cc
diff --git a/chrome_frame/chrome_active_document.cc b/chrome_frame/chrome_active_document.cc
index 6c16f13f439f5f5fcf44846ace9db66a3e3baf5c..03b2e316c69109b45b8439e5542c462cfbdf76aa 100644
--- a/chrome_frame/chrome_active_document.cc
+++ b/chrome_frame/chrome_active_document.cc
@@ -252,7 +252,7 @@ STDMETHODIMP ChromeActiveDocument::Load(BOOL fully_avalable,
     return E_INVALIDARG;
   }
 
-  std::string referrer(mgr ? mgr->referrer() : EmptyString());
+  std::string referrer(mgr ? mgr->referrer() : std::string());
   RendererType renderer_type = cf_url.is_chrome_protocol() ?
       RENDERER_TYPE_CHROME_GCF_PROTOCOL : RENDERER_TYPE_UNDETERMINED;
 
@@ -399,8 +399,7 @@ STDMETHODIMP ChromeActiveDocument::LoadHistory(IStream* stream,
     return E_INVALIDARG;
   }
 
-  const std::string& referrer = EmptyString();
-  if (!LaunchUrl(cf_url, referrer)) {
+  if (!LaunchUrl(cf_url, std::string())) {
     NOTREACHED() << __FUNCTION__ << " Failed to launch url:" << url;
     return E_INVALIDARG;
   }