Add an offset property to ol.Overlay

Replaces "offsetX" and "offsetY" by an ol.Object "offset" property.

externs/olx.js

@@ -203,12 +203,11 @@ olx.MapOptions.prototype.view;
 /**
  * Object literal with config options for the overlay.
  * @typedef {{element: (Element|undefined),
+ *     offset: (Array.<number>|undefined),
  *     position: (ol.Coordinate|undefined),
  *     positioning: (ol.OverlayPositioning|string|undefined),
  *     stopEvent: (boolean|undefined),
- *     insertFirst: (boolean|undefined),
- *     offsetX: (number|undefined),
- *     offsetY: (number|undefined)}}
+ *     insertFirst: (boolean|undefined)}}
  * @todo api
  */
 olx.OverlayOptions;
@@ -221,6 +220,16 @@ olx.OverlayOptions;
 olx.OverlayOptions.prototype.element;
 
 
+/**
+ * Offsets in pixels used when positioning the overlay. The fist element in the
+ * array is the horizontal offset. A positive value shifts the overlay right.
+ * The second element in the array is the vertical offset. A positive value
+ * shifts the overlay down. Default is `[0, 0]`.
+ * @type {Array.<number>|undefined}
+ */
+olx.OverlayOptions.prototype.offset;
+
+
 /**
  * The overlay position in map projection.
  * @type {ol.Coordinate|undefined}
@@ -254,22 +263,6 @@ olx.OverlayOptions.prototype.stopEvent;
 olx.OverlayOptions.prototype.insertFirst;
 
 
-/**
- * Horizontal offset in pixels. A positive will shift the overlay right. Default
- * is `0`.
- * @type {number|undefined}
- */
-olx.OverlayOptions.prototype.offsetX;
-
-
-/**
- * Vertical offset in pixels. A positive will shift the overlay down. Default is
- * `0`.
- * @type {number|undefined}
- */
-olx.OverlayOptions.prototype.offsetY;
-
-
 /**
  * Object literal with config options for the Proj4js projection.
  * @typedef {{code: string,