Removed unused thread checker.

components/autofill/browser/autofill_country.cc

Index: components/autofill/browser/autofill_country.cc
diff --git a/components/autofill/browser/autofill_country.cc b/components/autofill/browser/autofill_country.cc
index 26cc5caa20507c1af43fb48fbd9128ece828eba3..bae6541bd5ee925bb5c3ef05302ac8ff3a6062af 100644
--- a/components/autofill/browser/autofill_country.cc
+++ b/components/autofill/browser/autofill_country.cc
@@ -14,7 +14,6 @@
 #include "base/memory/singleton.h"
 #include "base/stl_util.h"
 #include "base/string_util.h"
-#include "base/threading/thread_checker.h"
 #include "base/utf_string_conversions.h"
 #include "grit/generated_resources.h"
 #include "third_party/icu/public/common/unicode/locid.h"
@@ -891,9 +890,6 @@ class CountryNames {
   // Maps ICU locale names to their corresponding collators.
   std::map<std::string, icu::Collator*> collators_;
 
-  // Verifies thread-safety of accesses to the application locale.
-  base::ThreadChecker thread_checker_;
-
   DISALLOW_COPY_AND_ASSIGN(CountryNames);
 };