Typo in SequenceCheckerImpl

Bug: 
Change-Id: Id45f9ef44b25aac984b1f444911a233457a630f5
Reviewed-on: https://chromium-review.googlesource.com/517550Reviewed-by: Gabriel Charette <gab@chromium.org>
Commit-Queue: Takeshi Yoshino <tyoshino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#475780}

base/sequence_checker_impl.cc

@@ -19,7 +19,7 @@ class SequenceCheckerImpl::Core {
         sequenced_worker_pool_token_(
             SequencedWorkerPool::GetSequenceTokenForCurrentThread()) {
     // SequencedWorkerPool doesn't use SequenceToken and code outside of
-    // SequenceWorkerPool doesn't set a SequencedWorkerPool token.
+    // SequencedWorkerPool doesn't set a SequencedWorkerPool token.
     DCHECK(!sequence_token_.IsValid() ||
            !sequenced_worker_pool_token_.IsValid());
   }