Add SetFileSize() IPC for WebSQL.

storage/browser/database/vfs_backend.cc

 // Copyright (c) 2011 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 "storage/browser/database/vfs_backend.h"
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
 #include "third_party/sqlite/sqlite3.h"
@@ skipping 137 matching lines @@
 #endif
   return attributes;
 }
 
 // static
 int64 VfsBackend::GetFileSize(const base::FilePath& file_path) {
   int64 size = 0;
   return (base::GetFileSize(file_path, &size) ? size : 0);
 }
 
+// static
+bool VfsBackend::SetFileSize(const base::FilePath& file_path, int64 size) {
+  int flags = 0;
+  flags |= base::File::FLAG_READ;
+  flags |= base::File::FLAG_WRITE;
+  flags |= base::File::FLAG_OPEN;
+  base::File file = base::File(file_path, flags);
+  if (!file.IsValid())
+    return false;
+  return file.SetLength(size);
+}
+
 }  // namespace storage