Register factories for ChromeAssistantUtilTest

When using IdentityTestEnvironmentProfileAdaptor, it is required
to register the testing factories when creating the Profile, as
the adaptor will expect the IdentityManager to have been created
with certain fakes.

If the factories are not set, then it is possible to encounter
Undefined Behaviour (as IdentityTestEnvironment cast some of the
objects to the expected fake subclasses) in the worst case or
just non-fonctioning test (calling undefined methods) on certain
platforms.

Fix ChromeAssistantUtilTest to use the proper factory.

Bug: 982751
Change-Id: Ic61a874b300cf36f3575f524a8bf7e57e0dc96b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1806741Reviewed-by: Tao Wu <wutao@chromium.org>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697542}

chrome/browser/chromeos/assistant/assistant_util_unittest.cc

@@ -149,7 +149,11 @@ class ChromeAssistantUtilTest : public testing::Test {
         TestingBrowserProcess::GetGlobal());
     ASSERT_TRUE(profile_manager_->SetUp());
 
-    profile_ = profile_manager_->CreateTestingProfile(kTestProfileName);
+    profile_ = profile_manager_->CreateTestingProfile(
+        kTestProfileName, /*prefs=*/{}, base::UTF8ToUTF16(kTestProfileName),
+        /*avatar_id=*/0, /*supervised_user_id=*/{},
+        IdentityTestEnvironmentProfileAdaptor::
+            GetIdentityTestEnvironmentFactories());
     identity_test_env_adaptor_ =
         std::make_unique<IdentityTestEnvironmentProfileAdaptor>(profile_);
     user_manager_enabler_ = std::make_unique<user_manager::ScopedUserManager>(