Provide chrome the option of learning the debug stub port chosen by nacl.

src/trusted/debug_stub/nacl_debug.cc

 /*
  * Copyright (c) 2012 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include <vector>
 #include <map>
 
@@ skipping 29 matching lines @@
 #pragma warning(disable:4530)
 #endif
 
 
 static Target *g_target = NULL;
 static SocketBinding *g_socket_binding = NULL;
 
 int NaClDebugBindSocket() {
   if (g_socket_binding == NULL) {
     NaClDebugStubInit();
-    const char *addr = "127.0.0.1:4014";
-    g_socket_binding = SocketBinding::Bind(addr);
+    // Try port 4014 first for compatibility.
+    g_socket_binding = SocketBinding::Bind("127.0.0.1:4014");
+    // If port 4014 is not available, try any port.
     if (g_socket_binding == NULL) {
-      NaClLog(LOG_ERROR, "NaClStubThread: Failed to bind TCP port '%s'\n",
-              addr);
+      g_socket_binding = SocketBinding::Bind("127.0.0.1:0");
+    }
+    if (g_socket_binding == NULL) {
+      NaClLog(LOG_ERROR,
+              "NaClDebugStubBindSocket: Failed to bind any TCP port\n");
       return 0;
     }
     NaClLog(LOG_WARNING,
-            "nacl_debug(%d) : Connect GDB with 'target remote %s'.\n",
-            __LINE__, addr);
+            "nacl_debug(%d) : Connect GDB with 'target remote :%d\n",
+            __LINE__, g_socket_binding->GetBoundPort());
   }
   return 1;
 }
 
 void NaClDebugSetBoundSocket(NaClSocketHandle bound_socket) {
   CHECK(g_socket_binding == NULL);
   g_socket_binding = new SocketBinding(bound_socket);
 }
 
 void WINAPI NaClStubThread(void *thread_arg) {
   UNREFERENCED_PARAMETER(thread_arg);
 
-  if (!NaClDebugBindSocket()) {
-    return;
-  }
   while (1) {
     // Wait for a connection.
     nacl::scoped_ptr<ITransport> trans(g_socket_binding->AcceptConnection());
     if (NULL == trans.get()) continue;
 
     // Create a new session for this connection
     Session ses(trans.get());
     ses.SetFlags(Session::DEBUG_MASK);
 
     NaClLog(LOG_WARNING, "nacl_debug(%d) : Connected, happy debugging!\n",
@@ skipping 32 matching lines @@
     NaClLog(LOG_ERROR, "NaClDebugInit: Failed to initialize fault handling\n");
     return 0;
   }
   nap->debug_stub_callbacks = &debug_callbacks;
 
   CHECK(g_target == NULL);
   g_target = new Target(nap);
   CHECK(g_target != NULL);
   g_target->Init();
 
+  if (!NaClDebugBindSocket()) {
+    return 0;
+  }
+  nap->debug_stub_port = g_socket_binding->GetBoundPort();
+
   NaClThread *thread = new NaClThread;
   CHECK(thread != NULL);
 
   NaClLog(LOG_WARNING, "nacl_debug(%d) : Debugging started.\n", __LINE__);
   CHECK(NaClThreadCtor(thread, NaClStubThread, NULL, NACL_KERN_STACK_SIZE));
 
   return 1;
 }