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

chrome/browser/chromeos/drive/webkit_file_stream_reader_impl_unittest.cc

Index: chrome/browser/chromeos/drive/webkit_file_stream_reader_impl_unittest.cc
diff --git a/chrome/browser/chromeos/drive/webkit_file_stream_reader_impl_unittest.cc b/chrome/browser/chromeos/drive/webkit_file_stream_reader_impl_unittest.cc
index 2132eaf71e64c312f47e32e80e9a98ec6e732124..1392ac55c3a640dc63cb721c9b2debd827e04cc1 100644
--- a/chrome/browser/chromeos/drive/webkit_file_stream_reader_impl_unittest.cc
+++ b/chrome/browser/chromeos/drive/webkit_file_stream_reader_impl_unittest.cc
@@ -52,13 +52,6 @@ class WebkitFileStreamReaderImplTest : public ::testing::Test {
     fake_file_system_->Initialize();
   }
 
-  virtual void TearDown() OVERRIDE {
-    fake_file_system_.reset();
-    fake_drive_service_.reset();
-
-    worker_thread_.reset();
-  }
-
   FileSystemInterface* GetFileSystem() {
     return fake_file_system_.get();
   }