Give isolates names to be used during debugging.

runtime/vm/dart.cc

Index: runtime/vm/dart.cc
===================================================================
--- runtime/vm/dart.cc	(revision 3366)
+++ runtime/vm/dart.cc	(working copy)
@@ -39,7 +39,7 @@
   {
     ASSERT(vm_isolate_ == NULL);
     ASSERT(Flags::Initialized());
-    vm_isolate_ = Isolate::Init();
+    vm_isolate_ = Isolate::Init("vm-isolate");
     Zone zone(vm_isolate_);
     HandleScope handle_scope(vm_isolate_);
     Heap::Init(vm_isolate_);
@@ -55,9 +55,9 @@
 }
 
 
-Isolate* Dart::CreateIsolate() {
+Isolate* Dart::CreateIsolate(const char* name_prefix) {
   // Create a new isolate.
-  Isolate* isolate = Isolate::Init();
+  Isolate* isolate = Isolate::Init(name_prefix);
   ASSERT(isolate != NULL);
   return isolate;
 }