Use event init dictionary in modules/device_light

Source/modules/device_light/DeviceLightEvent.idl

Index: Source/modules/device_light/DeviceLightEvent.idl
diff --git a/Source/modules/device_light/DeviceLightEvent.idl b/Source/modules/device_light/DeviceLightEvent.idl
index 6d3d3b9ed440f98a62dbca0d502f9163def1869d..6a1f13f9ae00195040771d0f1ea61d467ed95a5b 100644
--- a/Source/modules/device_light/DeviceLightEvent.idl
+++ b/Source/modules/device_light/DeviceLightEvent.idl
@@ -2,9 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// http://w3c.github.io/ambient-light/#idl-def-DeviceLightEvent
+
 [
     RuntimeEnabled=DeviceLight,
-    EventConstructor
+    Constructor(DOMString type, optional DeviceLightEventInit eventInitDict),
 ] interface DeviceLightEvent : Event {
-    [InitializedByEventConstructor] readonly attribute unrestricted double value;
+    readonly attribute unrestricted double value;
 };