make passes to be independent from each other

lib/svgo.js

@@ -24,6 +24,33 @@ var SVGO = module.exports = function(config) {
 
 SVGO.prototype.optimize = function(svgstr, callback) {
 
+    var _this = this,
+        config = this.config,
+        maxPassCount = config.multipass ? 10 : 1,
+        counter = 0,
+        prevResultSize = Number.POSITIVE_INFINITY,
+        optimizeOnceCallback = function(svgjs) {
+
+            if (svgjs.error) {
+                callback(svgjs);
+                return;
+            }
+
+            if (++counter < maxPassCount && svgjs.data.length < prevResultSize) {
+                prevResultSize = svgjs.data.length;
+                _this._optimizeOnce(svgjs.data, optimizeOnceCallback);
+            } else {
+                callback(svgjs);
+            }
+
+        };
+
+    _this._optimizeOnce(svgstr, optimizeOnceCallback);
+
+};
+
+SVGO.prototype._optimizeOnce = function(svgstr, callback) {
+
     var config = this.config;
 
     SVG2JS(svgstr, function(svgjs) {
@@ -33,24 +60,14 @@ SVGO.prototype.optimize = function(svgstr, callback) {
             return;
         }
 
-        var svg = { data : null },
+        svgjs = PLUGINS(svgjs, config.plugins);
-            maxIterationCount = config.multipass ? 10 : 1,
-            counter = 0,
-            prevResult;
 
-        do {
+        callback(JS2SVG(svgjs, config.js2svg));
-            prevResult = svg;
-            svgjs = PLUGINS(svgjs, config.plugins);
-            svg = JS2SVG(svgjs, config.js2svg);
-        } while(++counter < maxIterationCount && prevResult.data !== svg.data);
-
-        callback(svg);
 
     });
 
 };
 
-
 /**
  * The factory that creates a content item with the helper methods.
  *