fix($http): do not modify the config object passed into $http short methods

Update $http's createShortMethods and createShortMethodsWithData
to extend an empty object instead of the passed-in config.
Previously, since $http was extending the passed-in config,
the changes to the config object persisted even after the call to $http's
get/post/etc. returned. This causes unexpected behavior if that
config object is reused in subsequent calls to $http.
The existing test in httpSpec was not properly testing this situation.

Closes: #11764

Author: maxthyen

src/ng/http.js

@@ -1094,7 +1094,7 @@ function $HttpProvider() {
     function createShortMethods(names) {
       forEach(arguments, function(name) {
         $http[name] = function(url, config) {
-          return $http(extend(config || {}, {
+          return $http(extend({}, config || {}, {
             method: name,
             url: url
           }));
@@ -1106,7 +1106,7 @@ function $HttpProvider() {
     function createShortMethodsWithData(name) {
       forEach(arguments, function(name) {
         $http[name] = function(url, data, config) {
-          return $http(extend(config || {}, {
+          return $http(extend({}, config || {}, {
             method: name,
             url: url,
             data: data

test/ng/httpSpec.js

@@ -230,13 +230,16 @@ describe('$http', function() {
           });
         });
         inject(function($http, $httpBackend, $rootScope) {
-          var config = { method: 'get', url: '/url', headers: { foo: 'bar'} };
+          var config = { headers: { foo: 'bar'} };
+          var configCopy = angular.copy(config);
           $httpBackend.expect('GET', '/intercepted').respond('');
-          $http.get('/url');
+          $http.get('/url', config);
+          $rootScope.$apply();
+          expect(config).toEqual(configCopy);
+          $httpBackend.expect('POST', '/intercepted').respond('');
+          $http.post('/url', {bar: 'baz'}, config);
           $rootScope.$apply();
-          expect(config.method).toEqual('get');
-          expect(config.url).toEqual('/url');
-          expect(config.headers.foo).toEqual('bar');
+          expect(config).toEqual(configCopy);
         });
       });