Releasing the former Stadia file transfer tools

The tools allow efficient and fast synchronization of large directory
trees from a Windows workstation to a Linux target machine.

cdc_rsync* support efficient copy of files by using content-defined
chunking (CDC) to identify chunks within files that can be reused.

asset_stream_manager + cdc_fuse_fs support efficient streaming of a
local directory to a remote virtual file system based on FUSE. It also
employs CDC to identify and reuse unchanged data chunks.

common/scoped_handle_win.h

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2022 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef COMMON_SCOPED_HANDLE_WIN_H_
+#define COMMON_SCOPED_HANDLE_WIN_H_
+
+using HANDLE = void*;
+
+namespace cdc_ft {
+
+// In Windows, some functions return nullptr as invalid handles, some
+// INVALID_HANDLE_VALUE. This class attempts to minimize this pain.
+class ScopedHandle {
+ public:
+  ScopedHandle();
+
+  explicit ScopedHandle(HANDLE handle);
+
+  ScopedHandle(ScopedHandle&& other);
+
+  ~ScopedHandle();
+
+  ScopedHandle(const ScopedHandle&) = delete;
+  ScopedHandle& operator=(const ScopedHandle&) = delete;
+
+  bool IsValid() const;
+
+  ScopedHandle& operator=(ScopedHandle&& other);
+
+  void Set(HANDLE handle);
+
+  HANDLE Get() const;
+
+  // Transfers ownership away from this object.
+  HANDLE Release();
+
+  // Explicitly closes the owned handle.
+  void Close();
+
+ private:
+  static bool IsHandleValid(HANDLE handle);
+
+  HANDLE handle_;
+};
+
+}  // namespace cdc_ft
+
+#endif  // COMMON_SCOPED_HANDLE_WIN_H_