fix($httpBackend): Allow status code 0 from any protocol

Android 4.1 stock browser also returns status code 0 when
a template is loaded via `http` and the application is cached using
appcache.

Fixes angular#1356.
Closes angular#5547.

Author: rafallo

src/ng/httpBackend.js

@@ -121,14 +121,14 @@ function createHttpBackend($browser, createXhr, $browserDefer, callbacks, rawDoc
     }
 
     function completeRequest(callback, status, response, headersString) {
-      var protocol = urlResolve(url).protocol;
-
       // cancel timeout and subsequent timeout promise resolution
       timeoutId && $browserDefer.cancel(timeoutId);
       jsonpDone = xhr = null;
 
-      // fix status code for file protocol (it's always 0)
-      status = (protocol == 'file' && status === 0) ? (response ? 200 : 404) : status;
+      // fix status code when it is 0 (0 status is undocumented).
+      // Occurs when accessing file resources.
+      // On Android 4.1 stock browser it occurs while retrieving files from application cache.
+      status = (status === 0) ? (response ? 200 : 404) : status;
 
       // normalize IE bug (http://bugs.jquery.com/ticket/1450)
       status = status == 1223 ? 204 : status;

test/ng/httpBackendSpec.js

@@ -421,7 +421,7 @@ describe('$httpBackend', function() {
     // TODO(vojta): test whether it fires "async-end" on both success and error
   });
 
-  describe('file protocol', function() {
+  describe('protocols that return 0 status code', function() {
 
     function respond(status, content) {
       xhr = MockXhr.$$lastInstance;
@@ -435,7 +435,7 @@ describe('$httpBackend', function() {
     it('should convert 0 to 200 if content', function() {
       $backend = createHttpBackend($browser, createMockXhr);
 
-      $backend('GET', 'file:///whatever/index.html', null, callback);
+      $backend('GET', 'someProtocol:///whatever/index.html', null, callback);
       respond(0, 'SOME CONTENT');
 
       expect(callback).toHaveBeenCalled();
@@ -446,7 +446,7 @@ describe('$httpBackend', function() {
     it('should convert 0 to 404 if no content', function() {
       $backend = createHttpBackend($browser, createMockXhr);
 
-      $backend('GET', 'file:///whatever/index.html', null, callback);
+      $backend('GET', 'someProtocol:///whatever/index.html', null, callback);
       respond(0, '');
 
       expect(callback).toHaveBeenCalled();
@@ -462,10 +462,10 @@ describe('$httpBackend', function() {
         hash : "#/C:/",
         host : "",
         hostname : "",
-        href : "file:///C:/base#!/C:/foo",
+        href : "someProtocol:///C:/base#!/C:/foo",
         pathname : "/C:/foo",
         port : "",
-        protocol : "file:",
+        protocol : "someProtocol:",
         search : "",
         setAttribute: angular.noop
       };