add code comments to click and mousewheel handlers

src/ol/handler/Click.js

@@ -57,6 +57,7 @@ ol.handler.Click.prototype.disposeInternal = function() {
  * @param {goog.events.BrowserEvent} e
  */
 ol.handler.Click.prototype.handleClick = function(e) {
+    // do not emit a map click event after a drag
     if (!this.states_.dragged) {
         goog.events.dispatchEvent(this.map_, e);
     }

src/ol/handler/MouseWheel.js

@@ -76,5 +76,6 @@ ol.handler.MouseWheel.prototype.defaultBehavior = function(e) {
     map.setZoom(map.getZoom() - step, e.position);
 
     // We don't want the page to scroll.
+    // (MouseWheelEvent is a BrowserEvent)
     e.preventDefault();
 };