Do not require an extent for global projections

src/ol/proj/proj.js

@@ -120,9 +120,13 @@ ol.proj.Projection = function(options) {
    * @type {boolean}
    */
   this.global_ = goog.isDef(options.global) ? options.global : false;
-  if (this.global_) {
-    goog.asserts.assert(!goog.isNull(this.extent_));
-  }
+
+
+  /**
+   * @private
+   * @type {boolean}
+   */
+  this.canWrapX_ = this.global_ && !goog.isNull(this.extent_);
 
   /**
   * @private
@@ -175,6 +179,14 @@ ol.proj.Projection = function(options) {
 };
 
 
+/**
+ * @return {boolean} The projection is suitable for wrapping the x-axis
+ */
+ol.proj.Projection.prototype.canWrapX = function() {
+  return this.canWrapX_;
+};
+
+
 /**
  * Get the code for this projection, e.g. 'EPSG:4326'.
  * @return {string} Code.
@@ -258,6 +270,7 @@ ol.proj.Projection.prototype.isGlobal = function() {
 */
 ol.proj.Projection.prototype.setGlobal = function(global) {
   this.global_ = global;
+  this.canWrapX_ = global && !goog.isNull(this.extent_);
 };
 
 
@@ -284,6 +297,7 @@ ol.proj.Projection.prototype.setDefaultTileGrid = function(tileGrid) {
  */
 ol.proj.Projection.prototype.setExtent = function(extent) {
   this.extent_ = extent;
+  this.canWrapX_ = this.global_ && !goog.isNull(extent);
 };