Implement DeviceLight

Source/modules/device_light/DeviceLightDispatcher.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 DeviceLightDispatcher_h
+#define DeviceLightDispatcher_h
+
+#include "core/frame/DeviceSensorEventDispatcher.h"
+#include "public/platform/WebDeviceLightListener.h"
+#include "wtf/RefPtr.h"
+
+namespace WebCore {
+
+class DeviceLightController;
+
+// This class listens to device light data and dispatches it to all
+// listening controllers
+class DeviceLightDispatcher FINAL : public DeviceSensorEventDispatcher, public blink::WebDeviceLightListener {
+public:
+    static DeviceLightDispatcher& instance();
+
+    double latestDeviceLightData() const;
+
+    // This method is called every time new device light data is available.
+    virtual void didChangeDeviceLight(const double) OVERRIDE;
+    void addDeviceLightController(DeviceLightController*);
+    void removeDeviceLightController(DeviceLightController*);
+
+private:
+    DeviceLightDispatcher();
+    virtual ~DeviceLightDispatcher();
+
+    virtual void startListening() OVERRIDE;
+    virtual void stopListening() OVERRIDE;
+
+    double m_lastDeviceLightData;

[timvolodine, 2014/04/10 12:43:13]

is this initialized somewhere? preferably such that
DeviceLightController::hasLastData() returns false initially..

[riju_, 2014/04/10 14:10:41]

Done.
Initializing m_lastDeviceLightData = -1 in the c'stor because 0 is a valid Lux
value.

+};
+
+} // namespace WebCore
+
+#endif // DeviceLightDispatcher_h