Replace deprecated base::NonThreadSafe in extensions in favor of SequenceChecker.

extensions/browser/warning_service.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef EXTENSIONS_BROWSER_WARNING_SERVICE_H_
 #define EXTENSIONS_BROWSER_WARNING_SERVICE_H_
 
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/observer_list.h"
 #include "base/scoped_observer.h"
-#include "base/threading/non_thread_safe.h"
+#include "base/sequence_checker.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "extensions/browser/extension_registry_observer.h"
 #include "extensions/browser/warning_set.h"
 
 // TODO(battre) Remove the Extension prefix.
 
 namespace content {
 class BrowserContext;
 }
 
 namespace extensions {
 
 class ExtensionRegistry;
 
 // Manages a set of warnings caused by extensions. These warnings (e.g.
 // conflicting modifications of network requests by extensions, slow extensions,
 // etc.) trigger a warning badge in the UI and and provide means to resolve
 // them. This class must be used on the UI thread only.

[Devlin, 2017/05/30 19:06:47]

I'm not sure that SequenceChecker is right for this class (and not sure that
base::NonThreadSafe was entirely right, either).  This is designed to be used
specifically on the UI thread *only*, and uses UI-thread concepts
(BrowserContext and related).  I think what we want instead is to replace
CalledOnValidThread() or CALLED_ON_VALID_SEQUENCE with
DCHECK_CURRENTLY_ON(content::BrowserThread::UI) or ThreadChecker.

[gab, 2017/05/31 17:52:28]

Done.

-class WarningService : public KeyedService,
-                       public ExtensionRegistryObserver,
-                       public base::NonThreadSafe {
+class WarningService : public KeyedService, public ExtensionRegistryObserver {
  public:
   class Observer {
    public:
     virtual void ExtensionWarningsChanged(
         const ExtensionIdSet& affected_extensions) = 0;
   };
 
   // |browser_context| may be NULL for testing. In this case, be sure to not
   // insert any warnings.
   explicit WarningService(content::BrowserContext* browser_context);
@@ skipping 38 matching lines @@
   // Currently existing warnings.
   WarningSet warnings_;
 
   content::BrowserContext* const browser_context_;
 
   // Listen to extension unloaded notifications.
   ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
       extension_registry_observer_;
 
   base::ObserverList<Observer> observer_list_;
+
+  SEQUENCE_CHECKER(sequence_checker_);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_WARNING_SERVICE_H_