Remove destruction-only TearDown() methods in Drive related test.

chrome/browser/chromeos/drive/file_system/update_operation_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/chromeos/drive/file_system/update_operation.h"
 
 #include "chrome/browser/chromeos/drive/file_system/operation_test_base.h"
 #include "chrome/browser/chromeos/drive/file_system_interface.h"
 #include "chrome/browser/drive/fake_drive_service.h"
 #include "chrome/browser/google_apis/gdata_wapi_parser.h"
 #include "chrome/browser/google_apis/test_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace drive {
 namespace file_system {
 
 class UpdateOperationTest : public OperationTestBase {
  protected:
   virtual void SetUp() OVERRIDE {
    OperationTestBase::SetUp();
    operation_.reset(new UpdateOperation(blocking_task_runner(),
                                         observer(),
                                         scheduler(),
                                         metadata(),
                                         cache()));
  }
 
- virtual void TearDown() OVERRIDE {
-   operation_.reset();
-   OperationTestBase::TearDown();
- }
-
  scoped_ptr<UpdateOperation> operation_;
 };
 
 TEST_F(UpdateOperationTest, UpdateFileByResourceId_PersistentFile) {
   const base::FilePath kFilePath(FILE_PATH_LITERAL("drive/root/File 1.txt"));
   const std::string kResourceId("file:2_file_resource_id");
   const std::string kMd5("3b4382ebefec6e743578c76bbd0575ce");
 
   const base::FilePath kTestFile = temp_dir().Append(FILE_PATH_LITERAL("foo"));
   const std::string kTestFileContent = "I'm being uploaded! Yay!";
@@ skipping 57 matching lines @@
   operation_->UpdateFileByResourceId(
       "file:nonexistent_resource_id",
       ClientContext(USER_INITIATED),
       google_apis::test_util::CreateCopyResultCallback(&error));
   google_apis::test_util::RunBlockingPoolTask();
   EXPECT_EQ(FILE_ERROR_NOT_FOUND, error);
 }
 
 }  // namespace file_system
 }  // namespace drive