fix($templateRequest): ignore JSON Content-Type header and content

Normally, if there is a Content-Type header with the string "application/json", or else the content
looks sort of JSON-y, $http will attempt to deserialize the JSON into an object. $templateRequest
is intended to request markup, and as such should never attempt to parse JSON, regardless of the
headers or shape of the content.

Closes angular#5756

Author: caitp

src/ng/templateRequest.js

@@ -21,11 +21,16 @@ var $compileMinErr = minErr('$compile');
  */
 function $TemplateRequestProvider() {
   this.$get = ['$templateCache', '$http', '$q', function($templateCache, $http, $q) {
+    var httpOptions = {
+      cache: $templateCache,
+      transformResponse: null
+    };
+
     function handleRequestFn(tpl, ignoreRequestError) {
       var self = handleRequestFn;
       self.totalPendingRequests++;
 
-      return $http.get(tpl, { cache : $templateCache })
+      return $http.get(tpl, httpOptions)
         .then(function(response) {
           var html = response.data;
           if(!html || html.length === 0) {

test/ng/templateRequestSpec.js

@@ -86,4 +86,15 @@ describe('$templateRequest', function() {
     expect($templateRequest.totalPendingRequests).toBe(0);
   }));
 
+  it('should not try to parse a response as JSON',
+    inject(function($templateRequest, $httpBackend) {
+      var spy = jasmine.createSpy('success');
+      $httpBackend.expectGET('a.html').respond('{{text}}', {
+        'Content-Type': 'application/json'
+      });
+      $templateRequest('a.html').then(spy);
+      $httpBackend.flush();
+      expect(spy).toHaveBeenCalledOnce();
+      expect(spy.argsForCall[0][0]).toBe('{{text}}');
+  }));
 });