old_contents: (function() {
      // save these original methods before they are overwritten
      var proto_initIcon = L.Marker.prototype._initIcon;
      var proto_setPos = L.Marker.prototype._setPos;
  
      var oldIE = (L.DomUtil.TRANSFORM === 'msTransform');
  
      L.Marker.addInitHook(function () {
          var iconAnchor = this.options.icon.options.iconAnchor;
          if (iconAnchor) {
              iconAnchor = (iconAnchor[0] + 'px ' + iconAnchor[1] + 'px');
          }
          this.options.rotationOrigin = this.options.rotationOrigin || iconAnchor || 'center bottom' ;
          this.options.rotationAngle = this.options.rotationAngle || 0;
      });
  
      L.Marker.include({
          _initIcon: function() {
              proto_initIcon.call(this);
          },
  
          _setPos: function (pos) {
              proto_setPos.call(this, pos);
  
              if(this.options.rotationAngle) {
                  this._icon.style[L.DomUtil.TRANSFORM+'Origin'] = this.options.rotationOrigin;
  
                  if(oldIE) {
                      // for IE 9, use the 2D rotation
                      this._icon.style[L.DomUtil.TRANSFORM] = 'rotate(' + this.options.rotationAngle + 'deg)';
                  } else {
                      // for modern browsers, prefer the 3D accelerated version
                      this._icon.style[L.DomUtil.TRANSFORM] += ' rotateZ(' + this.options.rotationAngle + 'deg)';
                  }
              }
          },
  
          setRotationAngle: function(angle) {
              this.options.rotationAngle = angle;
              this.update();
              return this;
          },
  
          setRotationOrigin: function(origin) {
              this.options.rotationOrigin = origin;
              this.update();
              return this;
          }
      });
  })();
  
new_contents: (function() {
      // save these original methods before they are overwritten
      var proto_initIcon = L.Marker.prototype._initIcon;
      var proto_setPos = L.Marker.prototype._setPos;
  
      var oldIE = (L.DomUtil.TRANSFORM === 'msTransform');
  
      L.Marker.addInitHook(function () {
          var iconOptions = this.options.icon && this.options.icon.options;
          var iconAnchor = iconOptions && this.options.icon.options.iconAnchor;
          if (iconAnchor) {
              iconAnchor = (iconAnchor[0] + 'px ' + iconAnchor[1] + 'px');
          }
          this.options.rotationOrigin = this.options.rotationOrigin || iconAnchor || 'center bottom' ;
          this.options.rotationAngle = this.options.rotationAngle || 0;
      });
  
      L.Marker.include({
          _initIcon: function() {
              proto_initIcon.call(this);
          },
  
          _setPos: function (pos) {
              proto_setPos.call(this, pos);
  
              if(this.options.rotationAngle) {
                  this._icon.style[L.DomUtil.TRANSFORM+'Origin'] = this.options.rotationOrigin;
  
                  if(oldIE) {
                      // for IE 9, use the 2D rotation
                      this._icon.style[L.DomUtil.TRANSFORM] = 'rotate(' + this.options.rotationAngle + 'deg)';
                  } else {
                      // for modern browsers, prefer the 3D accelerated version
                      this._icon.style[L.DomUtil.TRANSFORM] += ' rotateZ(' + this.options.rotationAngle + 'deg)';
                  }
              }
          },
  
          setRotationAngle: function(angle) {
              this.options.rotationAngle = angle;
              this.update();
              return this;
          },
  
          setRotationOrigin: function(origin) {
              this.options.rotationOrigin = origin;
              this.update();
              return this;
          }
      });
  })();
  
subject: Check if icon is valid