fix(parseKeyValue): ignore properties in prototype chain.

Previously, properties (typically functions) in the prototype chain (Object.prototype) would shadow
query parameters, and cause them to be serialized incorrectly.

This CL guards against this by using hasOwnProperty() to ensure that only own properties are a concern.

Closes angular#8070
Fixes angular#8068

src/Angular.js

@@ -1105,7 +1105,7 @@ function parseKeyValue(/**string*/keyValue) {
       key = tryDecodeURIComponent(key_value[0]);
       if ( isDefined(key) ) {
         var val = isDefined(key_value[1]) ? tryDecodeURIComponent(key_value[1]) : true;
-        if (!obj[key]) {
+        if (!hasOwnProperty.call(obj, key)) {
           obj[key] = val;
         } else if(isArray(obj[key])) {
           obj[key].push(val);

test/AngularSpec.js

@@ -470,6 +470,13 @@ describe('angular', function() {
       expect(parseKeyValue('flag1&flag1=value&flag1=value2&flag1')).
       toEqual({flag1: [true,'value','value2',true]});
     });
+
+
+    it('should ignore properties higher in the prototype chain', function() {
+      expect(parseKeyValue('toString=123')).toEqual({
+        'toString': '123'
+      });
+    });
   });
 
   describe('toKeyValue', function() {