Use immediate callback runner in testing profile

Currently |TestingProfile| initializes Chrome OS Account Manager with
|chromeos::DelayNetworkCall|, which uses |NetworkHandler|.
It leads to crashes in tests which do not initialize |NetworkHandler|
properly. (This code path was not exercised before, but in
https://crrev.com/c/2232324 we start using Account Manager in tests
and some tests crash because of this issue.)

Fix this by not using |chromeos::DelayNetworkCall| and instead supplying
a fake runner which immediately executes its callbacks.

Bug: 1068240
Change-Id: I220ebc32fa069876f4cd607ba1bae89a35ac7d41
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2346350Reviewed-by: Kush Sinha <sinhak@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Commit-Queue: Anastasiia N <anastasiian@chromium.org>
Cr-Commit-Position: refs/heads/master@{#796760}

chrome/test/base/testing_profile.cc

@@ -364,11 +364,11 @@ void TestingProfile::Init() {
       g_browser_process->platform_part()->GetAccountManagerFactory();
   chromeos::AccountManager* account_manager =
       factory->GetAccountManager(profile_path_.value());
-  account_manager->Initialize(
-      profile_path_, GetURLLoaderFactory(),
-      base::BindRepeating(&chromeos::DelayNetworkCall,
-                          base::TimeDelta::FromMilliseconds(
-                              chromeos::kDefaultNetworkRetryDelayMS)));
+  chromeos::AccountManager::DelayNetworkCallRunner immediate_callback_runner =
+      base::BindRepeating(
+          [](base::OnceClosure closure) -> void { std::move(closure).Run(); });
+  account_manager->Initialize(profile_path_, GetURLLoaderFactory(),
+                              immediate_callback_runner);
   account_manager->SetPrefService(GetPrefs());
   if (!chromeos::CrosSettings::IsInitialized()) {
     scoped_cros_settings_test_helper_.reset(