perf($http): move xsrf cookie check to after cache check in $http

$http was previously checking cookies to find an xsrf-token prior to checking
the cache. This caused a performance penalty of about 2ms, which can be very
significant when loading hundreds of template instances on a page.

Fixes #7717

Author: mkawalec

src/ng/http.js

@@ -674,14 +674,6 @@ function $HttpProvider() {
       config.headers = headers;
       config.method = uppercase(config.method);
 
-      var xsrfValue = urlIsSameOrigin(config.url)
-          ? $browser.cookies()[config.xsrfCookieName || defaults.xsrfCookieName]
-          : undefined;
-      if (xsrfValue) {
-        headers[(config.xsrfHeaderName || defaults.xsrfHeaderName)] = xsrfValue;
-      }
-
-
       var serverRequest = function(config) {
         headers = config.headers;
         var reqData = transformData(config.data, headersGetter(headers), config.transformRequest);
@@ -957,8 +949,17 @@ function $HttpProvider() {
         }
       }
 
-      // if we won't have the response in cache, send the request to the backend
+
+      // if we won't have the response in cache, set the xsrf headers and
+      // send the request to the backend
       if (isUndefined(cachedResp)) {
+        var xsrfValue = urlIsSameOrigin(config.url)
+            ? $browser.cookies()[config.xsrfCookieName || defaults.xsrfCookieName]
+            : undefined;
+        if (xsrfValue) {
+          reqHeaders[(config.xsrfHeaderName || defaults.xsrfHeaderName)] = xsrfValue;
+        }
+
         $httpBackend(config.method, url, reqData, done, reqHeaders, config.timeout,
             config.withCredentials, config.responseType);
       }

test/ng/httpSpec.js

@@ -860,6 +860,25 @@ describe('$http', function() {
 
         $httpBackend.flush();
       }));
+
+      it('should check the cache before checking the XSRF cookie', inject(function($browser, $cacheFactory) {
+        var testCache = $cacheFactory('testCache'),
+            executionOrder = [];
+
+        spyOn($browser, 'cookies').andCallFake(function() {
+          executionOrder.push('cookies');
+          return {'XSRF-TOKEN':'foo'};
+        });
+        spyOn(testCache, 'get').andCallFake(function() {
+          executionOrder.push('cache');
+        });
+
+        $httpBackend.expect('GET', '/url', undefined).respond('');
+        $http({url: '/url', method: 'GET', cache: testCache});
+        $httpBackend.flush();
+
+        expect(executionOrder).toEqual(['cache', 'cookies']);
+      }));
     });