Generalize and refactor DeviceSensorEvent* architecture to support multi-event type targets.

Source/core/frame/DeviceEventDispatcherBase.h

+// 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.
+
+#ifndef DeviceEventDispatcherBase_h
+#define DeviceEventDispatcherBase_h
+
+#include "wtf/Vector.h"
+
+namespace WebCore {
+class DeviceEventControllerBase;
+
+class DeviceEventDispatcherBase {
+public:
+    void addController(DeviceEventControllerBase*);
+    void removeController(DeviceEventControllerBase*);
+
+protected:
+    DeviceEventDispatcherBase();
+    virtual ~DeviceEventDispatcherBase();
+
+    void notifyControllers();
+
+    virtual void startListening() = 0;
+    virtual void stopListening() = 0;
+
+private:
+    void purgeControllers();
+
+    Vector<DeviceEventControllerBase*> m_controllers;
+    bool m_needsPurge;
+    bool m_isDispatching;
+};
+
+} // namespace WebCore
+
+#endif // DeviceEventDispatcherBase_h