NOT INTENDED FOR LANDING: A promises demo

components/scheduler/promises/promise_executor.h

+// 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.
+
+#ifndef COMPONENTS_SCHEDULER_PROMISES_PROMISE_EXECUTOR_H_
+#define COMPONENTS_SCHEDULER_PROMISES_PROMISE_EXECUTOR_H_
+
+#include <set>
+
+#include "base/macros.h"
+#include "components/scheduler/promises/promise.h"
+#include "components/scheduler/scheduler_export.h"
+
+namespace promise {
+namespace internal {
+
+class SCHEDULER_EXPORT PromiseExecutor {
+ public:
+  PromiseExecutor();
+  virtual ~PromiseExecutor();
+
+  template <typename R>
+  void StartResolve(::promise::Promise<R>& promise) {
+    StartResolveInternal(promise.promise());
+  }
+
+  virtual void StartResolveInternal(internal::PromiseBase* promise);
+
+  // Returns true if some work was done.
+  bool ResolveOnePromise();
+
+  // Note this blocks.
+  void RunUntilIdle();
+
+ protected:
+  friend class PromiseBase;
+
+  PromiseBase* GetNextReadyPromise();
+  void ResolvePromise(PromiseBase* promise);
+
+  // Returns true if resolving |promise| means we can resolve more work.
+  virtual bool OnPromiseResolved(PromiseBase* promise);
+
+  // Returns true if rejecting |promise| means we can can run a reject callback.
+  virtual bool OnPromiseRejected(PromiseBase* promise);
+
+  std::set<PromiseBase*> eager_ready_set_;
+  std::set<PromiseBase*> lazy_ready_set_;
+  PromiseBase* cursor_;
+
+  DISALLOW_COPY_AND_ASSIGN(PromiseExecutor);
+};
+
+}  // namespace internal
+}  // namespace promise
+
+#endif  // COMPONENTS_SCHEDULER_PROMISES_PROMISE_EXECUTOR_H_