Replace deprecated base::NonThreadSafe in /content/browser/loader in favor of SequenceChecker.

content/browser/loader/resource_handler.h

Index: content/browser/loader/resource_handler.h
diff --git a/content/browser/loader/resource_handler.h b/content/browser/loader/resource_handler.h
index c292cab2312b73082c8531f8e9d8c705f05e6556..2b67e0c4c32870df71c51ada9c39fb3ad0f67780 100644
--- a/content/browser/loader/resource_handler.h
+++ b/content/browser/loader/resource_handler.h
@@ -18,7 +18,7 @@
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
-#include "base/threading/non_thread_safe.h"
+#include "base/sequence_checker.h"
 #include "content/browser/loader/resource_controller.h"
 #include "content/common/content_export.h"
 
@@ -43,8 +43,7 @@ struct ResourceResponse;
 // No ResourceHandler method other than OnWillRead will ever be called
 // synchronously when it calls into the ResourceController passed in to it,
 // either to resume or cancel the request.
-class CONTENT_EXPORT ResourceHandler
-    : public NON_EXPORTED_BASE(base::NonThreadSafe) {
+class CONTENT_EXPORT ResourceHandler {
  public:
   virtual ~ResourceHandler();
 
@@ -176,6 +175,8 @@ class CONTENT_EXPORT ResourceHandler
   Delegate* delegate_;
   std::unique_ptr<ResourceController> controller_;
 
+  SEQUENCE_CHECKER(sequence_checker_);
+
   DISALLOW_COPY_AND_ASSIGN(ResourceHandler);
 };