Add TaskPriority as a parameter to SequencedWorkerPool in preparation for TaskScheduler experiment.

components/webcrypto/webcrypto_impl.cc

 // Copyright 2014 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.
 
 #include "components/webcrypto/webcrypto_impl.h"
 
 #include <limits.h>
 #include <stdint.h>
 
 #include <memory>
@@ skipping 54 matching lines @@
 //
 // * blink::WebCryptoResult is not threadsafe and should only be operated on
 //   the target Blink thread. HOWEVER, it is safe to delete it from any thread.
 //   This can happen if by the time the operation has completed in the crypto
 //   worker pool, the Blink worker thread that initiated the request is gone.
 //   Posting back to the origin thread will fail, and the WebCryptoResult will
 //   be deleted while running in the crypto worker pool.
 class CryptoThreadPool {
  public:
   CryptoThreadPool()
-      : worker_pool_(new base::SequencedWorkerPool(1, "WebCrypto")),
+      : worker_pool_(
+            new base::SequencedWorkerPool(1,
+                                          "WebCrypto",
+                                          base::TaskPriority::USER_BLOCKING)),
         task_runner_(worker_pool_->GetSequencedTaskRunnerWithShutdownBehavior(
             worker_pool_->GetSequenceToken(),
             base::SequencedWorkerPool::CONTINUE_ON_SHUTDOWN)) {}
 
   static bool PostTask(const tracked_objects::Location& from_here,
                        const base::Closure& task);
 
  private:
   scoped_refptr<base::SequencedWorkerPool> worker_pool_;
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
@@ skipping 695 matching lines @@
       webcrypto::CryptoData(key_data, key_data_size), &key);
 }
 
 bool WebCryptoImpl::serializeKeyForClone(
     const blink::WebCryptoKey& key,
     blink::WebVector<unsigned char>& key_data) {
   return webcrypto::SerializeKeyForClone(key, &key_data);
 }
 
 }  // namespace webcrypto