Updated toJson() to not serialize window/document objects.

The reason to void these to objects is that they cause all sorts
of problems like exceptions being thrown and infinite loops occuring
when we iterate over object properties.

src/JSON.js

@@ -22,8 +22,18 @@ function fromJson(json) {
 angular['toJson'] = toJson;
 angular['fromJson'] = fromJson;
 
-function toJsonArray(buf, obj, pretty, stack){
-  if (typeof obj == "object") {
+function toJsonArray(buf, obj, pretty, stack) {
+  if (isObject(obj)) {
+    if (obj === window) {
+      buf.push('WINDOW');
+      return;
+    }
+
+    if (obj === document) {
+      buf.push('DOCUMENT');
+      return;
+    }
+
     if (includes(stack, obj)) {
       buf.push("RECURSION");
       return;

test/JsonSpec.js

@@ -92,6 +92,14 @@ describe('json', function(){
   it('should not serialize undefined values', function() {
     expect(angular.toJson({A:undefined})).toEqual('{}');
   });
+  
+  it('should not serialize $window object', function() {
+    expect(toJson(window)).toEqual('WINDOW');
+  });
+  
+  it('should not serialize $document object', function() {
+    expect(toJson(document)).toEqual('DOCUMENT');
+  });
 
   it('should parse floats', function() {
     expect(fromJson("{value:2.55, name:'misko'}")).toEqual({value:2.55, name:'misko'});