Add truncation to StreamCopyOrMoveImpl and test case.

webkit/browser/fileapi/copy_or_move_operation_delegate.cc

 // Copyright (c) 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 "webkit/browser/fileapi/copy_or_move_operation_delegate.h"
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
@@ skipping 405 matching lines @@
     }
 
     if (file_info.is_directory) {
       // If not a directory, failed with appropriate error code.
       callback.Run(base::File::FILE_ERROR_NOT_A_FILE);
       return;
     }
 
     // To use FileStreamWriter, we need to ensure the destination file exists.
     operation_runner_->CreateFile(
-        dest_url_, false /* exclusive */,
+        dest_url_,
+        true /* exclusive */,
         base::Bind(&StreamCopyOrMoveImpl::RunAfterCreateFileForDestination,
                    weak_factory_.GetWeakPtr(),
-                   callback, file_info.last_modified));
+                   callback,
+                   file_info.last_modified));
   }
 
   void RunAfterCreateFileForDestination(
       const CopyOrMoveOperationDelegate::StatusCallback& callback,
       const base::Time& last_modified,
       base::File::Error error) {
     if (cancel_requested_)
       error = base::File::FILE_ERROR_ABORT;
 
+    if (error != base::File::FILE_OK &&
+        error != base::File::FILE_ERROR_EXISTS) {
+      callback.Run(error);
+      return;
+    }
+
+    if (error == base::File::FILE_ERROR_EXISTS) {
+      operation_runner_->Truncate(
+          dest_url_,
+          0 /* length */,
+          base::Bind(&StreamCopyOrMoveImpl::RunAfterTruncateForDestination,
+                     weak_factory_.GetWeakPtr(),
+                     callback,
+                     last_modified));
+      return;
+    }
+    RunAfterTruncateForDestination(
+        callback, last_modified, base::File::FILE_OK);
+  }
+
+  void RunAfterTruncateForDestination(
+      const CopyOrMoveOperationDelegate::StatusCallback& callback,
+      const base::Time& last_modified,
+      base::File::Error error) {
+    if (cancel_requested_)
+      error = base::File::FILE_ERROR_ABORT;
+
     if (error != base::File::FILE_OK) {
       callback.Run(error);
       return;
     }
 
     const bool need_flush = dest_url_.mount_option().copy_sync_option() ==
                             storage::COPY_SYNC_OPTION_SYNC;
 
     DCHECK(!copy_helper_);
     copy_helper_.reset(
@@ skipping 508 matching lines @@
   base::FilePath relative = dest_root_.virtual_path();
   src_root_.virtual_path().AppendRelativePath(src_url.virtual_path(),
                                               &relative);
   return file_system_context()->CreateCrackedFileSystemURL(
       dest_root_.origin(),
       dest_root_.mount_type(),
       relative);
 }
 
 }  // namespace storage