Revert of Remove header dependencies from sequence_checker.h to sequenced_worker_pool.h

base/sequence_checker_impl.cc

Index: base/sequence_checker_impl.cc
diff --git a/base/sequence_checker_impl.cc b/base/sequence_checker_impl.cc
index df2a8cb24fef58b68633745afd723705ac1455f7..b8e87e6d4249c50c72662498c019f56e4fbb5e2b 100644
--- a/base/sequence_checker_impl.cc
+++ b/base/sequence_checker_impl.cc
@@ -5,65 +5,54 @@
 #include "base/sequence_checker_impl.h"
 
 #include "base/logging.h"
-#include "base/memory/ptr_util.h"
-#include "base/sequence_token.h"
-#include "base/threading/sequenced_worker_pool.h"
-#include "base/threading/thread_checker_impl.h"
 
 namespace base {
 
-class SequenceCheckerImpl::Core {
- public:
-  Core()
-      : sequence_token_(SequenceToken::GetForCurrentThread()),
-        sequenced_worker_pool_token_(
-            SequencedWorkerPool::GetSequenceTokenForCurrentThread()) {
-    // SequencedWorkerPool doesn't use SequenceToken and code outside of
-    // SequenceWorkerPool doesn't set a SequencedWorkerPool token.
-    DCHECK(!sequence_token_.IsValid() ||
-           !sequenced_worker_pool_token_.IsValid());
-  }
+SequenceCheckerImpl::SequenceCheckerImpl() {
+  AutoLock auto_lock(lock_);
+  EnsureSequenceTokenAssigned();
+}
 
-  ~Core() = default;
-
-  bool CalledOnValidThread() const {
-    if (sequence_token_.IsValid())
-      return sequence_token_ == SequenceToken::GetForCurrentThread();
-
-    if (sequenced_worker_pool_token_.IsValid()) {
-      return sequenced_worker_pool_token_.Equals(
-          SequencedWorkerPool::GetSequenceTokenForCurrentThread());
-    }
-
-    // SequenceChecker behaves as a ThreadChecker when it is not bound to a
-    // valid sequence token.
-    return thread_checker_.CalledOnValidThread();
-  }
-
- private:
-  SequenceToken sequence_token_;
-
-  // TODO(gab): Remove this when SequencedWorkerPool is deprecated in favor of
-  // TaskScheduler. crbug.com/622400
-  SequencedWorkerPool::SequenceToken sequenced_worker_pool_token_;
-
-  // Used when |sequenced_worker_pool_token_| and |sequence_token_| are invalid.
-  ThreadCheckerImpl thread_checker_;
-};
-
-SequenceCheckerImpl::SequenceCheckerImpl() : core_(MakeUnique<Core>()) {}
 SequenceCheckerImpl::~SequenceCheckerImpl() = default;
 
 bool SequenceCheckerImpl::CalledOnValidSequence() const {
   AutoLock auto_lock(lock_);
-  if (!core_)
-    core_ = MakeUnique<Core>();
-  return core_->CalledOnValidThread();
+  EnsureSequenceTokenAssigned();
+
+  if (sequence_token_.IsValid())
+    return sequence_token_ == SequenceToken::GetForCurrentThread();
+
+  if (sequenced_worker_pool_token_.IsValid()) {
+    return sequenced_worker_pool_token_.Equals(
+        SequencedWorkerPool::GetSequenceTokenForCurrentThread());
+  }
+
+  // SequenceChecker behaves as a ThreadChecker when it is not bound to a valid
+  // sequence token.
+  return thread_checker_.CalledOnValidThread();
 }
 
 void SequenceCheckerImpl::DetachFromSequence() {
   AutoLock auto_lock(lock_);
-  core_.reset();
+  is_assigned_ = false;
+  sequence_token_ = SequenceToken();
+  sequenced_worker_pool_token_ = SequencedWorkerPool::SequenceToken();
+  thread_checker_.DetachFromThread();
+}
+
+void SequenceCheckerImpl::EnsureSequenceTokenAssigned() const {
+  lock_.AssertAcquired();
+  if (is_assigned_)
+    return;
+
+  is_assigned_ = true;
+  sequence_token_ = SequenceToken::GetForCurrentThread();
+  sequenced_worker_pool_token_ =
+      SequencedWorkerPool::GetSequenceTokenForCurrentThread();
+
+  // SequencedWorkerPool doesn't use SequenceToken and code outside of
+  // SequenceWorkerPool doesn't set a SequencedWorkerPool token.
+  DCHECK(!sequence_token_.IsValid() || !sequenced_worker_pool_token_.IsValid());
 }
 
 }  // namespace base