Revert 211956 "base: Change WeakPtr to use SequenceChecker inste..."

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 e95b8ee5f3e25e639a609e5cb0c5aad291fe6e59..24d9ed99a147c7c5a8d2db69557b3f891851cfa4 100644
--- a/base/sequence_checker_impl.cc
+++ b/base/sequence_checker_impl.cc
@@ -4,43 +4,28 @@
 
 #include "base/sequence_checker_impl.h"
 
+#include "base/sequenced_task_runner.h"
+
 namespace base {
 
-SequenceCheckerImpl::SequenceCheckerImpl()
-    : sequence_token_assigned_(false) {
-  AutoLock auto_lock(lock_);
-  EnsureSequenceTokenAssigned();
-}
+SequenceCheckerImpl::SequenceCheckerImpl(
+    const scoped_refptr<SequencedTaskRunner>& sequenced_task_runner)
+    : sequenced_task_runner_(sequenced_task_runner) {}
 
 SequenceCheckerImpl::~SequenceCheckerImpl() {}
 
-bool SequenceCheckerImpl::CalledOnValidSequencedThread() const {
+bool SequenceCheckerImpl::CalledOnValidSequence() const {
   AutoLock auto_lock(lock_);
-  EnsureSequenceTokenAssigned();
-
-  // If this thread is not associated with a SequencedWorkerPool,
-  // SequenceChecker behaves as a ThreadChecker. See header for details.
-  if (!sequence_token_.IsValid())
-    return thread_checker_.CalledOnValidThread();
-
-  return sequence_token_.Equals(
-      SequencedWorkerPool::GetSequenceTokenForCurrentThread());
+  return sequenced_task_runner_.get() ?
+      sequenced_task_runner_->RunsTasksOnCurrentThread() :
+      thread_checker_.CalledOnValidThread();
 }
 
-void SequenceCheckerImpl::DetachFromSequence() {
+void SequenceCheckerImpl::ChangeSequence(
+    const scoped_refptr<SequencedTaskRunner>& sequenced_task_runner) {
   AutoLock auto_lock(lock_);
+  sequenced_task_runner_ = sequenced_task_runner;
   thread_checker_.DetachFromThread();
-  sequence_token_assigned_ = false;
-  sequence_token_ = SequencedWorkerPool::SequenceToken();
-}
-
-void SequenceCheckerImpl::EnsureSequenceTokenAssigned() const {
-  lock_.AssertAcquired();
-  if (sequence_token_assigned_)
-    return;
-
-  sequence_token_assigned_ = true;
-  sequence_token_ = SequencedWorkerPool::GetSequenceTokenForCurrentThread();
 }
 
 }  // namespace base