diff -r 000000000000 -r 6474c204b198 dom/interfaces/events/nsIDOMDeviceOrientationEvent.idl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/interfaces/events/nsIDOMDeviceOrientationEvent.idl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsIDOMEvent.idl"
+
+[scriptable, builtinclass, uuid(f5921a77-3ac5-4374-bc0c-1ed52fe83123)]
+interface nsIDOMDeviceOrientationEvent : nsIDOMEvent
+{
+  void initDeviceOrientationEvent(in DOMString eventTypeArg,
+                                  in boolean canBubbleArg,
+                                  in boolean cancelableArg,
+                                  in double alpha,
+                                  in double beta,
+                                  in double gamma,
+                                  in boolean absolute);
+
+  /*
+   * W3C specification values: http://dev.w3.org/geo/api/spec-source-orientation.html
+   *
+   * Alpha, beta and gamma are Tait-Bryan angles (Z-X'-Y''), that is they correspond to
+   * yaw, pitch and roll in flight coordinates. More specifically, assume the device
+   * is resting face up on a flat surface (its screen is pointing straight up). Then
+   * the X axis points to the right when looking at the screen, the Y axis points up
+   * when looking at the screen, and the Z axis points toward you when looking at
+   * the screen. Alpha/beta/gamma then define the device's orientation by applying
+   * the following rotations to the device in order:
+   *
+   * 1) Rotate it by alpha degrees around its Z axis (like a compass, or like changing
+   *    the yaw of an aircraft, assuming the Y axis is the nose of the craft); alpha
+   *    is in [0,360).
+   * 2) Rotate it by beta degrees around its X axis (tilting the top of the device
+   *    towards or away from you, like pitching an aircraft); beta is in [-180,180).
+   * 3) Rotate it by gamma degrees around its Y axis (tilting it sideways, like
+   *    rolling an aircraft); gamma is in [-90,90).
+   */
+
+  readonly attribute double alpha;
+  readonly attribute double beta;
+  readonly attribute double gamma;
+  readonly attribute boolean absolute;
+};