Lazy initialize OneGoogleBarFetcherImpl in OneGoogleBarFetcherImplTest

This is a preparation CL to migrate
OneGoogleBarFetcherImpl::AuthenticatedURLFetcher from using URLFetcher
to SimpleURLLoader.

In practice, when creating an OneGoogleBarFetcherImpl instance, we need
to pass the |api_url_override| as a parameter. When running SimpleURLLoader and
EmbeddedTestServer (for unit testing), we can only set the proper
|api_url_override| value after EmbeddedTestServer is instantiated, which
will happen from ::SetUp (see [1]).

This CL prepares the ground for it. No functionality change.

[1] https://crrev.com/c/1031450/

BUG=773295

Change-Id: Iebd0d8dc0134a343e5187812982b6b5570f3ebe3
Reviewed-on: https://chromium-review.googlesource.com/1035862
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555354}

chrome/browser/search/one_google_bar/one_google_bar_fetcher_impl_unittest.cc

@@ -82,16 +82,22 @@ class OneGoogleBarFetcherImplTest : public testing::Test {
             new net::TestURLRequestContextGetter(task_runner_)),
         google_url_tracker_(std::make_unique<GoogleURLTrackerClientStub>(),
                             GoogleURLTracker::ALWAYS_DOT_COM_MODE),
-        one_google_bar_fetcher_(request_context_getter_.get(),
-                                &google_url_tracker_,
-                                kApplicationLocale,
-                                api_url_override,
-                                account_consistency_mirror_required) {}
+        api_url_override_(api_url_override),
+        account_consistency_mirror_required_(
+            account_consistency_mirror_required) {}
 
   ~OneGoogleBarFetcherImplTest() override {
     static_cast<KeyedService&>(google_url_tracker_).Shutdown();
   }
 
+  void SetUp() override {
+    testing::Test::SetUp();
+
+    one_google_bar_fetcher_ = std::make_unique<OneGoogleBarFetcherImpl>(
+        request_context_getter_.get(), &google_url_tracker_, kApplicationLocale,
+        api_url_override_, account_consistency_mirror_required_);
+  }
+
   net::TestURLFetcher* GetRunningURLFetcher() {
     // All created URLFetchers have ID 0 by default.
     net::TestURLFetcher* url_fetcher = url_fetcher_factory_.GetFetcherByID(0);
@@ -123,7 +129,7 @@ class OneGoogleBarFetcherImplTest : public testing::Test {
   }
 
   OneGoogleBarFetcherImpl* one_google_bar_fetcher() {
-    return &one_google_bar_fetcher_;
+    return one_google_bar_fetcher_.get();
   }
 
  private:
@@ -140,7 +146,9 @@ class OneGoogleBarFetcherImplTest : public testing::Test {
   scoped_refptr<net::TestURLRequestContextGetter> request_context_getter_;
   GoogleURLTracker google_url_tracker_;
 
-  OneGoogleBarFetcherImpl one_google_bar_fetcher_;
+  base::Optional<std::string> api_url_override_;
+  bool account_consistency_mirror_required_;
+  std::unique_ptr<OneGoogleBarFetcherImpl> one_google_bar_fetcher_;
 };
 
 TEST_F(OneGoogleBarFetcherImplTest, RequestUrlContainsLanguage) {