Move EmptyString, kWhitespace and the BOM to base.

net/url_request/url_request_test_util.cc

Index: net/url_request/url_request_test_util.cc
diff --git a/net/url_request/url_request_test_util.cc b/net/url_request/url_request_test_util.cc
index d7fb151235914499a277212c7d876030a852bd0b..ea3c7ae60740326a60d30422aa976a187ecf5d9c 100644
--- a/net/url_request/url_request_test_util.cc
+++ b/net/url_request/url_request_test_util.cc
@@ -120,7 +120,7 @@ void TestURLRequestContext::Init() {
   }
   if (!http_user_agent_settings()) {
     context_storage_.set_http_user_agent_settings(
-        new StaticHttpUserAgentSettings("en-us,fr", EmptyString()));
+        new StaticHttpUserAgentSettings("en-us,fr", std::string()));
   }
   if (!job_factory())
     context_storage_.set_job_factory(new URLRequestJobFactoryImpl);