base: Get rid of 'using' declaration of StringAppendF.

chrome/service/net/service_url_request_context.cc

Index: chrome/service/net/service_url_request_context.cc
diff --git a/chrome/service/net/service_url_request_context.cc b/chrome/service/net/service_url_request_context.cc
index 1df288d7ee1d43b8e3d0131a74db494a5c773ea8..c7268f5b34154e19ce7df4b5700613153a3fa6f9 100644
--- a/chrome/service/net/service_url_request_context.cc
+++ b/chrome/service/net/service_url_request_context.cc
@@ -55,7 +55,7 @@ std::string BuildOSCpuInfo() {
   }
 #endif
 
-  StringAppendF(
+  base::StringAppendF(
       &os_cpu,
 #if defined(OS_WIN)
       "Windows NT %d.%d",
@@ -91,12 +91,12 @@ std::string MakeUserAgentForServiceProcess() {
   std::string extra_version_info;
   if (!version_info.IsOfficialBuild())
     extra_version_info = "-devel";
-  StringAppendF(&user_agent,
-                "Chrome Service %s(%s)%s %s ",
-                version_info.Version().c_str(),
-                version_info.LastChange().c_str(),
-                extra_version_info.c_str(),
-                BuildOSCpuInfo().c_str());
+  base::StringAppendF(&user_agent,
+                      "Chrome Service %s(%s)%s %s ",
+                      version_info.Version().c_str(),
+                      version_info.LastChange().c_str(),
+                      extra_version_info.c_str(),
+                      BuildOSCpuInfo().c_str());
   return user_agent;
 }