Distinguish transport threads.

Use "<-" and "->" to work around Linux's very short thread name limit.

Bug: http://b/23423333
Change-Id: I9f3f096415b47162dacb660cd0a97ac7ff6107e6
diff --git a/adb/transport.cpp b/adb/transport.cpp
index bd3bf16..43691dc 100644
--- a/adb/transport.cpp
+++ b/adb/transport.cpp
@@ -193,7 +193,7 @@
     atransport *t = reinterpret_cast<atransport*>(_t);
     apacket *p;
 
-    adb_thread_setname("to transport");
+    adb_thread_setname(android::base::StringPrintf("->%s", t->serial));
     D("%s: starting transport output thread on fd %d, SYNC online (%d)\n",
        t->serial, t->fd, t->sync_token + 1);
     p = get_apacket();
@@ -250,7 +250,7 @@
     apacket *p;
     int active = 0;
 
-    adb_thread_setname("from transport");
+    adb_thread_setname(android::base::StringPrintf("<-%s", t->serial));
     D("%s: starting transport input thread, reading from fd %d\n",
        t->serial, t->fd);