adb: implement zstd compression for file sync.

Bug: http://b/150827486
Test: test_device.py
Change-Id: I9fac4c760d9dbdce0b3b883db975cfa9b27a9e80
diff --git a/adb/test_device.py b/adb/test_device.py
index 9f1f403..c1caafc 100755
--- a/adb/test_device.py
+++ b/adb/test_device.py
@@ -1362,6 +1362,10 @@
     compression = "lz4"
 
 
+class FileOperationsTestZstd(FileOperationsTest.Base):
+    compression = "zstd"
+
+
 class DeviceOfflineTest(DeviceTest):
     def _get_device_state(self, serialno):
         output = subprocess.check_output(self.device.adb_cmd + ['devices'])