fix(test_lib): don't mock out XHR via MockXHR by default in tests

This is useful for the compiler tests, but otherwise it's not useful.

Additionally if an application has external templates (as is common) then
we should actually fetch these templates in tests.

Fixes angular#4539

Closes angular#4682

Author: IgorMinar

modules/angular2/src/test_lib/test_injector.ts

@@ -30,7 +30,6 @@ import {
 
 import {MockDirectiveResolver} from 'angular2/src/mock/directive_resolver_mock';
 import {MockViewResolver} from 'angular2/src/mock/view_resolver_mock';
-import {MockXHR} from 'angular2/src/core/compiler/xhr_mock';
 import {MockLocationStrategy} from 'angular2/src/mock/mock_location_strategy';
 import {LocationStrategy} from 'angular2/src/router/location_strategy';
 import {MockNgZone} from 'angular2/src/mock/ng_zone_mock';
@@ -116,7 +115,7 @@ function _getAppBindings() {
     PipeResolver,
     provide(ExceptionHandler, {asValue: new ExceptionHandler(DOM)}),
     provide(LocationStrategy, {asClass: MockLocationStrategy}),
-    provide(XHR, {asClass: MockXHR}),
+    XHR,
     TestComponentBuilder,
     provide(NgZone, {asClass: MockNgZone}),
     provide(AnimationBuilder, {asClass: MockAnimationBuilder}),

modules/angular2/test/core/compiler/test_bindings.ts

@@ -1,6 +1,10 @@
 import {provide, Provider} from 'angular2/src/core/di';
 import {MockSchemaRegistry} from './schema_registry_mock';
 import {ElementSchemaRegistry} from 'angular2/src/core/compiler/schema/element_schema_registry';
+import {MockXHR} from 'angular2/src/core/compiler/xhr_mock';
+import {XHR} from 'angular2/src/core/compiler/xhr';
 
-export var TEST_PROVIDERS =
-    [provide(ElementSchemaRegistry, {asValue: new MockSchemaRegistry({}, {})})];
+export var TEST_PROVIDERS = [
+  provide(ElementSchemaRegistry, {asValue: new MockSchemaRegistry({}, {})}),
+  provide(XHR, {asClass: MockXHR})
+];