Update some uses of UTF conversions in chrome/browser to use the base:: namespace.

chrome/browser/signin/about_signin_internals.cc

Index: chrome/browser/signin/about_signin_internals.cc
diff --git a/chrome/browser/signin/about_signin_internals.cc b/chrome/browser/signin/about_signin_internals.cc
index cdec3dba9c6e156b66b28ccf4a1d72e796baf25e..d3af87b76522e4f5b03acc1c1a85f641b71bcd79 100644
--- a/chrome/browser/signin/about_signin_internals.cc
+++ b/chrome/browser/signin/about_signin_internals.cc
@@ -59,7 +59,8 @@ void AboutSigninInternals::NotifySigninValueChanged(
          field_index < signin_status_.timed_signin_fields.size());
 
   Time now = Time::NowFromSystemTime();
-  std::string time_as_str = UTF16ToUTF8(base::TimeFormatFriendlyDate(now));
+  std::string time_as_str =
+      base::UTF16ToUTF8(base::TimeFormatFriendlyDate(now));
   TimedSigninStatusValue timed_value(value, time_as_str);
 
   signin_status_.timed_signin_fields[field_index] = timed_value;