Add UpdateOperationTest for drive::file_system::UpdateOperationTest.

chrome/browser/chromeos/drive/file_system/operation_test_base.h

Index: chrome/browser/chromeos/drive/file_system/operation_test_base.h
diff --git a/chrome/browser/chromeos/drive/file_system/operation_test_base.h b/chrome/browser/chromeos/drive/file_system/operation_test_base.h
index 4fbe5cf53de7d2f09f13bd6bcd9b7876d11cbd14..fb1b6c2a5846718b260baf0928bc5404e1d460b8 100644
--- a/chrome/browser/chromeos/drive/file_system/operation_test_base.h
+++ b/chrome/browser/chromeos/drive/file_system/operation_test_base.h
@@ -68,6 +68,9 @@ class OperationTestBase : public testing::Test {
   virtual void SetUp() OVERRIDE;
   virtual void TearDown() OVERRIDE;
 
+  // Returns the path of the temporary directory for putting test files.
+  base::FilePath temp_dir() const { return temp_dir_.path(); }
+
   // Synchronously gets the resource entry corresponding to the path from local
   // ResourceMetadta.
   FileError GetLocalResourceEntry(const base::FilePath& path,