Add a task_scheduler tracing category which will record an extra event per task.

base/sequence_token.cc

 // Copyright 2016 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 "base/sequence_token.h"
 
 #include "base/atomic_sequence_num.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/threading/thread_local.h"
 
 namespace base {
 
 namespace {
 
 base::StaticAtomicSequenceNumber g_sequence_token_generator;
 
 base::StaticAtomicSequenceNumber g_task_token_generator;
 
@@ skipping 10 matching lines @@
 }
 
 bool SequenceToken::operator!=(const SequenceToken& other) const {
   return !(*this == other);
 }
 
 bool SequenceToken::IsValid() const {
   return token_ != kInvalidSequenceToken;
 }
 
+std::string SequenceToken::ToString() const {
+  return IntToString(token_);
+}
+
 SequenceToken SequenceToken::Create() {
   return SequenceToken(g_sequence_token_generator.GetNext());
 }
 
 SequenceToken SequenceToken::GetForCurrentThread() {
   const SequenceToken* current_sequence_token =
       tls_current_sequence_token.Get().Get();
   return current_sequence_token ? *current_sequence_token : SequenceToken();
 }
 
@@ skipping 29 matching lines @@
 
 ScopedSetSequenceTokenForCurrentThread::
     ~ScopedSetSequenceTokenForCurrentThread() {
   DCHECK_EQ(tls_current_sequence_token.Get().Get(), &sequence_token_);
   DCHECK_EQ(tls_current_task_token.Get().Get(), &task_token_);
   tls_current_sequence_token.Get().Set(nullptr);
   tls_current_task_token.Get().Set(nullptr);
 }
 
 }  // namespace base