adb: implement zstd compression for file sync.

Bug: http://b/150827486
Test: test_device.py
Change-Id: I9fac4c760d9dbdce0b3b883db975cfa9b27a9e80
diff --git a/transport.cpp b/transport.cpp
index 1667011..b6b6984 100644
--- a/transport.cpp
+++ b/transport.cpp
@@ -85,6 +85,7 @@
 const char* const kFeatureSendRecv2 = "sendrecv_v2";
 const char* const kFeatureSendRecv2Brotli = "sendrecv_v2_brotli";
 const char* const kFeatureSendRecv2LZ4 = "sendrecv_v2_lz4";
+const char* const kFeatureSendRecv2Zstd = "sendrecv_v2_zstd";
 const char* const kFeatureSendRecv2DryRunSend = "sendrecv_v2_dry_run_send";
 
 namespace {
@@ -1189,6 +1190,7 @@
                 kFeatureSendRecv2,
                 kFeatureSendRecv2Brotli,
                 kFeatureSendRecv2LZ4,
+                kFeatureSendRecv2Zstd,
                 kFeatureSendRecv2DryRunSend,
                 // Increment ADB_SERVER_VERSION when adding a feature that adbd needs
                 // to know about. Otherwise, the client can be stuck running an old