d3.layout.pie: return arcs in original data order.

Fixes d3#406.

d3.layout.js

@@ -638,9 +638,11 @@ d3.layout.pie = function() {
     });
 
     // Return the arcs in the original data's order.
-    return data.map(function(d, i) {
-      return arcs[index[i]];
+    data = [];
+    arcs.forEach(function(arc, i) {
+      data[index[i]] = arc;
     });
+    return data;
   }
 
   /**

src/layout/pie.js

@@ -37,9 +37,11 @@ d3.layout.pie = function() {
     });
 
     // Return the arcs in the original data's order.
-    return data.map(function(d, i) {
-      return arcs[index[i]];
+    data = [];
+    arcs.forEach(function(arc, i) {
+      data[index[i]] = arc;
     });
+    return data;
   }
 
   /**

test/layout/pie-test.js

@@ -0,0 +1,26 @@
+require("../env");
+require("../../d3");
+require("../../d3.layout");
+
+var vows = require("vows"),
+    assert = require("assert");
+
+var suite = vows.describe("d3.layout.pie");
+
+suite.addBatch({
+  "pie": {
+    topic: d3.layout.pie,
+    "arcs are in same order as original data": function(pie) {
+      assert.deepEqual(pie([5, 30, 15]).map(function(d) { return d.data; }), [
+        5, 30, 15
+      ]);
+      assert.deepEqual(pie([
+        84, 90, 48, 61, 58, 8, 6, 31, 45, 18
+      ]).map(function(d) { return d.data; }), [
+        84, 90, 48, 61, 58, 8, 6, 31, 45, 18
+      ]);
+    }
+  }
+});
+
+suite.export(module);