Replace deprecated base::NonThreadSafe in chrome/browser/ssl in favor of SequenceChecker.

chrome/browser/ssl/ssl_error_handler.cc

Index: chrome/browser/ssl/ssl_error_handler.cc
diff --git a/chrome/browser/ssl/ssl_error_handler.cc b/chrome/browser/ssl/ssl_error_handler.cc
index 2bbdd3ef364c715d7112e7180d6c2da545c876c2..a446078e390d2adfe1c9c3a950fdf1bf4e757342 100644
--- a/chrome/browser/ssl/ssl_error_handler.cc
+++ b/chrome/browser/ssl/ssl_error_handler.cc
@@ -16,7 +16,6 @@
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/stringprintf.h"
-#include "base/threading/non_thread_safe.h"
 #include "base/time/clock.h"
 #include "base/time/time.h"
 #include "chrome/browser/browser_process.h"
@@ -168,7 +167,7 @@ bool IsSSLCommonNameMismatchHandlingEnabled() {
 }
 
 // Configuration for SSLErrorHandler.
-class ConfigSingleton : public base::NonThreadSafe {
+class ConfigSingleton {
  public:
   ConfigSingleton();