Reland "Add --serial-id option to host_forwarder."

tools/android/forwarder2/daemon.cc

Index: tools/android/forwarder2/daemon.cc
diff --git a/tools/android/forwarder2/daemon.cc b/tools/android/forwarder2/daemon.cc
index d99383446c819ec4893af0b72d0adaa1a86863c3..88ec8a01ab7547210d2a995fd3891144837d6699 100644
--- a/tools/android/forwarder2/daemon.cc
+++ b/tools/android/forwarder2/daemon.cc
@@ -141,7 +141,7 @@ scoped_ptr<Socket> ConnectToUnixDomainSocket(
     char buf[kBufferSize];
     DCHECK(expected_welcome_message.length() + 1 <= sizeof(buf));
     memset(buf, 0, sizeof(buf));
-    if (socket->Read(buf, sizeof(buf)) < 0) {
+    if (socket->Read(buf, expected_welcome_message.length() + 1) < 0) {
       perror("read");
       continue;
     }