Require FilePathWatcher destructor to be called in sequence with Watch().

chrome/browser/media_galleries/fileapi/itunes_file_util_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 "chrome/browser/media_galleries/fileapi/itunes_file_util.h"
 
 #include <set>
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 171 matching lines @@
 
     file_system_context_ = new storage::FileSystemContext(
         base::ThreadTaskRunnerHandle::Get().get(),
         base::ThreadTaskRunnerHandle::Get().get(),
         storage::ExternalMountPoints::CreateRefCounted().get(),
         storage_policy.get(), NULL, std::move(additional_providers),
         std::vector<storage::URLRequestAutoMountHandler>(),
         profile_dir_.GetPath(), content::CreateAllowFileAccessOptions());
   }
 
+  void TearDown() override {
+    MediaFileSystemBackend::MediaTaskRunner()->DeleteSoon(
+        FROM_HERE, itunes_data_provider_.release());
+  }
+
  protected:
   void TestNonexistentFolder(const std::string& path_append) {
     FileSystemOperation::FileEntryList contents;
     FileSystemURL url = CreateURL(path_append);
     bool completed = false;
     ReadDirectoryTestHelper(operation_runner(), url, &contents, &completed);
 
     ASSERT_FALSE(completed);
   }
 
@@ skipping 141 matching lines @@
   completed = false;
   ReadDirectoryTestHelper(operation_runner(), url, &contents, &completed);
   ASSERT_TRUE(completed);
   ASSERT_EQ(1u, contents.size());
   EXPECT_FALSE(contents.front().is_directory);
   EXPECT_EQ(base::FilePath().AppendASCII("baz.ogg").value(),
             contents.front().name);
 }
 
 }  // namespace itunes