Make HistoryDataStoreTest and SearchHistoryTest's SequencedWorkerPool multi-threaded.

ui/app_list/search/history_data_store_unittest.cc

 // Copyright 2013 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/bind.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 23 matching lines @@
     str += *it;
   }
 
   return str;
 }
 
 }  // namespace
 
 class HistoryDataStoreTest : public testing::Test {
  public:
-  HistoryDataStoreTest() : worker_pool_owner_(1, "AppLanucherTest") {}
+  HistoryDataStoreTest() : worker_pool_owner_(2, "AppLanucherTest") {}

[Matt Giuca, 2016/09/15 23:54:20]

Same.

[gab, 2016/09/16 00:54:41]

Same.

 
   // testing::Test overrides:
   void SetUp() override {
     ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());
   }
   void TearDown() override {
     // Release |store_| while ui loop is still running.
     store_ = NULL;
   }
 
@@ skipping 115 matching lines @@
   EXPECT_EQ(now, it->second.update_time);
 
   store()->Delete(kQuery);
   Flush();
   Load();
   EXPECT_TRUE(associations().empty());
 }
 
 }  // namespace test
 }  // namespace app_list