NOT INTENDED FOR LANDING: A promises demo

components/scheduler/promises/thread_pool_promise_executor.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 "components/scheduler/promises/thread_pool_promise_executor.h"
+
+#include "base/bind.h"
+#include "base/threading/worker_pool.h"
+
+namespace promise {
+namespace internal {
+
+ThreadPoolPromiseExecutor::ThreadPoolPromiseExecutor() {}
+
+ThreadPoolPromiseExecutor::~ThreadPoolPromiseExecutor() {}
+
+void ThreadPoolPromiseExecutor::StartResolveInternal(PromiseBase* promise) {
+  PromiseExecutor::StartResolveInternal(promise);
+  DispatchExecutorDrivenResolve();
+}
+
+void ThreadPoolPromiseExecutor::ExecutorDrivenResolve() {
+  PromiseBase* ready_promise;
+  {
+    base::AutoLock lock(lock_);
+    ready_promise = GetNextReadyPromise();
+    DCHECK(ready_promise->state() != PromiseBase::State::RESOLVED);
+    DCHECK(ready_promise->AllPrerequisitesSatisfied());
+  }
+
+  if (!ready_promise)
+    return;
+
+  ready_promise->ExecutorDrivenResolve();
+}
+
+void ThreadPoolPromiseExecutor::DispatchExecutorDrivenResolve() {
+  base::WorkerPool::PostTask(
+      FROM_HERE, base::Bind(&ThreadPoolPromiseExecutor::ExecutorDrivenResolve,
+                            base::Unretained(this)),
+      true);
+}
+
+bool ThreadPoolPromiseExecutor::OnPromiseResolved(PromiseBase* promise) {
+  if (PromiseExecutor::OnPromiseResolved(promise))
+    DispatchExecutorDrivenResolve();
+  return false;
+}
+
+bool ThreadPoolPromiseExecutor::OnPromiseRejected(PromiseBase* promise) {
+  if (PromiseExecutor::OnPromiseRejected(promise))
+    DispatchExecutorDrivenResolve();
+  return false;
+}
+
+}  // namespace internal
+}  // namespace promise