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

extensions/browser/value_store/value_store_frontend.cc

Index: extensions/browser/value_store/value_store_frontend.cc
diff --git a/extensions/browser/value_store/value_store_frontend.cc b/extensions/browser/value_store/value_store_frontend.cc
index 964fdbe022a5387a9822335d0088335a7d79113d..05128f874c448576d7c1bc9755dbe382257ac12b 100644
--- a/extensions/browser/value_store/value_store_frontend.cc
+++ b/extensions/browser/value_store/value_store_frontend.cc
@@ -112,12 +112,12 @@ ValueStoreFrontend::ValueStoreFrontend(
     : backend_(new Backend(store_factory, backend_type)) {}
 
 ValueStoreFrontend::~ValueStoreFrontend() {
-  DCHECK(CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 }
 
 void ValueStoreFrontend::Get(const std::string& key,
                              const ReadCallback& callback) {
-  DCHECK(CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 
   BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,
       base::Bind(&ValueStoreFrontend::Backend::Get,
@@ -126,7 +126,7 @@ void ValueStoreFrontend::Get(const std::string& key,
 
 void ValueStoreFrontend::Set(const std::string& key,
                              std::unique_ptr<base::Value> value) {
-  DCHECK(CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 
   BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,
       base::Bind(&ValueStoreFrontend::Backend::Set,
@@ -134,7 +134,7 @@ void ValueStoreFrontend::Set(const std::string& key,
 }
 
 void ValueStoreFrontend::Remove(const std::string& key) {
-  DCHECK(CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 
   BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,
       base::Bind(&ValueStoreFrontend::Backend::Remove,