Caching bounds center location. r=elemoine (closes #1814)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@8286 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/BaseTypes/Bounds.js

@@ -38,7 +38,14 @@ OpenLayers.Bounds = OpenLayers.Class({
      * Property: top
      * {Number} Maximum vertical coordinate.
      */
-    top: null,    
+    top: null,
+    
+    /**
+     * Property: centerLonLat
+     * {<OpenLayers.LonLat>} A cached center location.  This should not be
+     *     accessed directly.  Use <getCenterLonLat> instead.
+     */
+    centerLonLat: null,
 
     /**
      * Constructor: OpenLayers.Bounds
@@ -215,8 +222,12 @@ OpenLayers.Bounds = OpenLayers.Class({
      * {<OpenLayers.LonLat>} The center of the bounds in map space.
      */
     getCenterLonLat:function() {
-        return new OpenLayers.LonLat( (this.left + this.right) / 2,
-                                      (this.bottom + this.top) / 2);
+        if(!this.centerLonLat) {
+            this.centerLonLat = new OpenLayers.LonLat(
+                (this.left + this.right) / 2, (this.bottom + this.top) / 2
+            );
+        }
+        return this.centerLonLat;
     },
 
     /**
@@ -257,7 +268,7 @@ OpenLayers.Bounds = OpenLayers.Class({
         var bottom = (this.bottom - origy) * ratio + origy;
         var right = (this.right - origx) * ratio + origx;
         var top = (this.top - origy) * ratio + origy;
-
+        
         return new OpenLayers.Bounds(left, bottom, right, top);
     },
 
@@ -291,8 +302,9 @@ OpenLayers.Bounds = OpenLayers.Class({
      * object - {Object} Can be LonLat, Point, or Bounds
      */
     extend:function(object) {
-        var bounds = null;
         if (object) {
+            // clear cached center location
+            this.centerLonLat = null;
             switch(object.CLASS_NAME) {
                 case "OpenLayers.LonLat":    
                     bounds = new OpenLayers.Bounds(object.lon, object.lat,
@@ -309,6 +321,7 @@ OpenLayers.Bounds = OpenLayers.Class({
             }
     
             if (bounds) {
+                var bounds = null;
                 if ( (this.left == null) || (bounds.left < this.left)) {
                     this.left = bounds.left;
                 }
@@ -499,6 +512,8 @@ OpenLayers.Bounds = OpenLayers.Class({
      * {<OpenLayers.Bounds>} Itself, for use in chaining operations.
      */
     transform: function(source, dest) {
+        // clear cached center location
+        this.centerLonLat = null;
         var ll = OpenLayers.Projection.transform(
             {'x': this.left, 'y': this.bottom}, source, dest);
         var lr = OpenLayers.Projection.transform(