Tiny: Post PerformFullHashCheck on IO thread, instead of calling it synchronously.

components/safe_browsing_db/v4_local_database_manager_unittest.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/files/scoped_temp_dir.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/run_loop.h"
 #include "base/test/test_simple_task_runner.h"
 #include "components/safe_browsing_db/v4_database.h"
@@ skipping 187 matching lines @@
   WaitForTasksOnTaskRunner();
   net::TestURLFetcherFactory factory;
 
   StoreAndHashPrefixes store_and_hash_prefixes;
   store_and_hash_prefixes.emplace_back(GetUrlMalwareId(), HashPrefix("aaaa"));
   ReplaceV4Database(store_and_hash_prefixes);
 
   // The fake database returns a matched hash prefix.
   EXPECT_FALSE(v4_local_database_manager_->CheckBrowseUrl(
       GURL("http://example.com/a/"), nullptr));
+
+  // Wait for PerformFullHashCheck to complete.
+  WaitForTasksOnTaskRunner();
 }
 
 TEST_F(V4LocalDatabaseManagerTest,
        TestCheckBrowseUrlReturnsNoMatchWhenDisabled) {
   WaitForTasksOnTaskRunner();
 
   // The same URL returns |false| in the previous test because
   // v4_local_database_manager_ is enabled.
   ForceDisableLocalDatabaseManager();
 
@@ skipping 44 matching lines @@
   ResetV4Database();
   v4_local_database_manager_->CheckBrowseUrl(url, &client);
   // The database is unavailable so the check should get queued.
   EXPECT_EQ(1ul, GetQueuedChecks().size());
 
   StopLocalDatabaseManager();
   EXPECT_TRUE(GetQueuedChecks().empty());
 }
 
 }  // namespace safe_browsing