refactor(toJson): remove breaking change from previous CL

Closes angular#10297

Author: caitp

src/Angular.js

@@ -970,7 +970,10 @@ function toJsonReplacer(key, value) {
  */
 function toJson(obj, pretty) {
   if (typeof obj === 'undefined') return undefined;
-  return JSON.stringify(obj, toJsonReplacer, pretty === true ? 2 : pretty);
+  if (!isNumber(pretty)) {
+    pretty = pretty ? 2 : null;
+  }
+  return JSON.stringify(obj, toJsonReplacer, pretty);
 }
 
 

test/AngularSpec.js

@@ -1189,7 +1189,7 @@ describe('angular', function() {
     });
 
 
-    iit('should format objects pretty', function() {
+    it('should format objects pretty', function() {
       expect(toJson({a: 1, b: 2}, true)).
           toBe('{\n  "a": 1,\n  "b": 2\n}');
       expect(toJson({a: {b: 2}}, true)).
@@ -1200,6 +1200,8 @@ describe('angular', function() {
           toBe('{"a":1,"b":2}');
       expect(toJson({a: 1, b: 2}, 1)).
           toBe('{\n "a": 1,\n "b": 2\n}');
+      expect(toJson({a: 1, b: 2}, {})).
+          toBe('{\n  "a": 1,\n  "b": 2\n}');
     });