[sensors]: Introduce the Generic Sensor API.

third_party/WebKit/Source/modules/sensor/Sensor.idl

+// 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.
+
+// Specification at:
+// https://w3c.github.io/sensors/#sensor0
+
+enum SensorState {
+  "idle",
+  "activating",
+  "active",
+  "errored"
+};
+
+[
+    RuntimeEnabled=Sensor,
+] interface Sensor : EventTarget {
+    readonly attribute SensorState state;
+    readonly attribute SensorReading? reading;
+
+    [CallWith=ScriptState, RaisesException] void start();
+    [CallWith=ScriptState, RaisesException] void stop();
+
+    attribute EventHandler onerror;
+    attribute EventHandler onchange;
+    attribute EventHandler onstatechange;
+};