Implement Device Orientation using shared memory in content/renderer.

content/renderer/device_orientation/device_sensor_event_pump.h

+// Copyright 2013 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 CONTENT_RENDERER_DEVICE_SENSOR_EVENT_PUMP_H_
+#define CONTENT_RENDERER_DEVICE_SENSOR_EVENT_PUMP_H_
+
+#include "base/memory/shared_memory.h"
+#include "base/timer/timer.h"
+#include "content/public/renderer/render_process_observer.h"
+
+namespace content {
+class RenderThread;
+
+class CONTENT_EXPORT DeviceSensorEventPump : public RenderProcessObserver {
+ public:
+  // Default delay between subsequent firing of events.
+  static const int kDefaultPumpDelayMillis;
+
+  int GetDelayMillis() const;
+
+  void Attach(RenderThread* thread);
+  virtual bool OnControlMessageReceived(const IPC::Message& message) = 0;
+
+ protected:
+  // Constructor for a pump with default delay.
+  DeviceSensorEventPump();
+
+  // Constructor for a pump with a given delay.
+  explicit DeviceSensorEventPump(int pump_delay_millis);
+  virtual ~DeviceSensorEventPump();
+
+  // The pump is a tri-state automaton with allowed transitions as follows:
+  // STOPPED -> PENDING_START
+  // PENDING_START -> RUNNING
+  // PENDING_START -> STOPPED
+  // RUNNING -> STOPPED
+  enum PumpState {
+      STOPPED,
+      RUNNING,
+      PENDING_START
+  };
+
+  bool RequestStart();
+  void OnDidStart(base::SharedMemoryHandle handle);
+  bool Stop();
+
+  virtual void FireEvent() = 0;
+  virtual bool InitializeReader(base::SharedMemoryHandle handle) = 0;
+  virtual bool SendStartMessage() = 0;
+  virtual bool SendStopMessage() = 0;
+
+  int pump_delay_millis_;
+  PumpState state_;
+  base::RepeatingTimer<DeviceSensorEventPump> timer_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_DEVICE_SENSOR_EVENT_PUMP_H_