Give isolates names to be used during debugging.

runtime/vm/port.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/port.h"
 
 #include "platform/utils.h"
 #include "vm/dart_api_impl.h"
 #include "vm/isolate.h"
 #include "vm/thread.h"
 
 namespace dart {
 
+DECLARE_FLAG(bool, trace_isolates);
 
 Mutex* PortMap::mutex_ = NULL;
 
 PortMap::Entry* PortMap::map_ = NULL;
 Isolate* PortMap::deleted_entry_ = reinterpret_cast<Isolate*>(1);
 intptr_t PortMap::capacity_ = 0;
 intptr_t PortMap::used_ = 0;
 intptr_t PortMap::deleted_ = 0;
 
 Dart_Port PortMap::next_port_ = 7111;
@@ skipping 188 matching lines @@
   ASSERT(index < capacity_);
   Isolate* isolate = map_[index].isolate;
   ASSERT(map_[index].port != 0);
   ASSERT((isolate != NULL) && (isolate != deleted_entry_));
 
   // Delegate message delivery to the embedder.
   Dart_PostMessageCallback callback = isolate->post_message_callback();
   ASSERT(callback);
   bool result =
       (*callback)(Api::CastIsolate(isolate), dest_port, reply_port, message);
-
+  if (FLAG_trace_isolates) {
+    const char* source_name = "<native code>";
+    Isolate* source_isolate = Isolate::Current();
+    if (source_isolate) {
+      source_name = source_isolate->name();
+    }
+    OS::Print("[>] Posting message:\n"
+              "\tsource:     %s\n"
+              "\treply_port: %lld\n"
+              "\tdest:       %s\n"
+              "\tdest_port:  %lld\n",
+              source_name, reply_port, isolate->name(), dest_port);
+  }
   mutex_->Unlock();
   return result;
 }
 
 
 void PortMap::InitOnce() {
   mutex_ = new Mutex();
 
   static const intptr_t kInitialCapacity = 8;
   // TODO(iposva): Verify whether we want to keep exponentially growing.
   ASSERT(Utils::IsPowerOfTwo(kInitialCapacity));
   map_ = new Entry[kInitialCapacity];
   memset(map_, 0, kInitialCapacity * sizeof(Entry));
   capacity_ = kInitialCapacity;
   used_ = 0;
   deleted_ = 0;
 }
 
 
 }  // namespace dart