Add base:: to string16s in chrome/.

chrome/app/metro_driver_win.cc

Index: chrome/app/metro_driver_win.cc
diff --git a/chrome/app/metro_driver_win.cc b/chrome/app/metro_driver_win.cc
index a5627113582cd4aaa245547881bab42af168de1b..faaff881bb8ea0419476de3c2875752900036945 100644
--- a/chrome/app/metro_driver_win.cc
+++ b/chrome/app/metro_driver_win.cc
@@ -46,7 +46,7 @@ MetroDriver::MetroDriver() : init_metro_fn_(NULL) {
     // It is not next to the build output, so this must be an actual deployment
     // and in that case we need the mainloader to find the current version
     // directory.
-    string16 version(GetCurrentModuleVersion());
+    base::string16 version(GetCurrentModuleVersion());
     if (!version.empty()) {
       std::wstring exe_path(GetExecutablePath());
       exe_path.append(version).append(L"\\").append(chrome::kMetroDriverDll);