Cache bounds and be smarter about reassigning marker properties

js/iD/Way.js

@@ -32,6 +32,7 @@ iD.Way.prototype = {
     addNode: function(node) {
         node.entity.addParent(this);
         this.nodes.push(node);
+        this._bounds = null;
         return this;
     },
 
@@ -63,9 +64,14 @@ iD.Way.prototype = {
         };
     },
 
+    updateBounds: function() {
+        this._bounds = d3.geo.bounds(this.toGeoJSON());
+    },
+
     bounds: function() {
         // TODO: cache
-        return d3.geo.bounds(this.toGeoJSON());
+        if (!this._bounds) this.updateBounds();
+        return this._bounds;
     },
 
     // ---------------------

js/iD/renderer/Map.js

@@ -261,10 +261,12 @@ iD.Map = function(obj) {
             .attr('class', classes('stroke'));
 
         markers.enter().append('image')
-            .on('click', selectClick);
-        markers.attr('class', classes('marker'))
+            .attr('class', classes('marker'))
+            .on('click', selectClick)
             .attr({ width: 16, height: 16 })
-            .attr('xlink:href', markerimage)
+            .attr('xlink:href', markerimage);
+
+        markers
             .attr('transform', function(d) {
                 return 'translate(' + projection(d) + ')';
             });