Revert of Use TaskScheduler instead of WorkerPool in v8_platform.cc.

gin/v8_platform.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 "gin/public/v8_platform.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/sys_info.h"
-#include "base/task_scheduler/post_task.h"
-#include "base/task_scheduler/task_scheduler.h"
+#include "base/threading/worker_pool.h"
 #include "base/trace_event/trace_event.h"
 #include "gin/per_isolate_data.h"
 
 namespace gin {
 
 namespace {
 
 base::LazyInstance<V8Platform>::Leaky g_v8_platform = LAZY_INSTANCE_INITIALIZER;
 
 void RunWithLocker(v8::Isolate* isolate, v8::Task* task) {
@@ skipping 14 matching lines @@
     task_->Run(deadline_in_seconds);
   }
 
  private:
   v8::Isolate* isolate_;
   std::unique_ptr<v8::IdleTask> task_;
 
   DISALLOW_COPY_AND_ASSIGN(IdleTaskWithLocker);
 };
 
-base::TaskTraits GetBackgroundThreadTaskTraits() {
-  return base::TaskTraits().WithShutdownBehavior(
-      base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN);
-}
-
 }  // namespace
 
 // static
 V8Platform* V8Platform::Get() { return g_v8_platform.Pointer(); }
 
 V8Platform::V8Platform() {}
 
 V8Platform::~V8Platform() {}
 
 size_t V8Platform::NumberOfAvailableBackgroundThreads() {
-  return base::TaskScheduler::GetInstance()
-      ->GetMaxConcurrentTasksWithTraitsDeprecated(
-          GetBackgroundThreadTaskTraits());
+  // WorkerPool will currently always create additional threads for posted
+  // background tasks, unless there are threads sitting idle (on posix).
+  // Indicate that V8 should create no more than the number of cores available,
+  // reserving one core for the main thread.
+  const size_t available_cores =
+    static_cast<size_t>(base::SysInfo::NumberOfProcessors());
+  if (available_cores > 1) {
+    return available_cores - 1;
+  }
+  return 1;
 }
 
 void V8Platform::CallOnBackgroundThread(
     v8::Task* task,
     v8::Platform::ExpectedRuntime expected_runtime) {
-  base::PostTaskWithTraits(FROM_HERE, GetBackgroundThreadTaskTraits(),
-                           base::Bind(&v8::Task::Run, base::Owned(task)));
+  base::WorkerPool::PostTask(
+      FROM_HERE,
+      base::Bind(&v8::Task::Run, base::Owned(task)),
+      expected_runtime == v8::Platform::kLongRunningTask);
 }
 
 void V8Platform::CallOnForegroundThread(v8::Isolate* isolate, v8::Task* task) {
   PerIsolateData* data = PerIsolateData::From(isolate);
   if (data->access_mode() == IsolateHolder::kUseLocker) {
     data->task_runner()->PostTask(
         FROM_HERE, base::Bind(RunWithLocker, base::Unretained(isolate),
                               base::Owned(task)));
   } else {
     data->task_runner()->PostTask(
@@ skipping 173 matching lines @@
     v8::Platform::TraceStateObserver* observer) {
   g_trace_state_dispatcher.Get().AddObserver(observer);
 }
 
 void V8Platform::RemoveTraceStateObserver(
     v8::Platform::TraceStateObserver* observer) {
   g_trace_state_dispatcher.Get().RemoveObserver(observer);
 }
 
 }  // namespace gin