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/stopwatch_test.cc

@@ -0,0 +1,47 @@
+// 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.
+
+#include "common/stopwatch.h"
+
+#include "common/testing_clock.h"
+#include "gtest/gtest.h"
+
+namespace cdc_ft {
+namespace {
+
+class StopwatchTest : public ::testing::Test {};
+
+TEST_F(StopwatchTest, DefaultStopwatch) {
+  // Cover DefaultClock.
+  Stopwatch stopwatch;
+  EXPECT_GE(stopwatch.ElapsedSeconds(), 0.0);
+}
+
+TEST_F(StopwatchTest, Stopwatch) {
+  TestingSteadyClock clock;
+  Stopwatch stopwatch(&clock);
+
+  EXPECT_EQ(stopwatch.ElapsedSeconds(), 0.0);
+  clock.Advance(1000);
+  EXPECT_EQ(stopwatch.ElapsedSeconds(), 1.0);
+  clock.Advance(500);
+  EXPECT_EQ(stopwatch.ElapsedSeconds(), 1.5);
+  stopwatch.Reset();
+  EXPECT_EQ(stopwatch.ElapsedSeconds(), 0.0);
+  clock.Advance(250);
+  EXPECT_EQ(stopwatch.ElapsedSeconds(), 0.25);
+}
+
+}  // namespace
+}  // namespace cdc_ft