Cleanup the exceptions create code to use Arrays instead GrowableArrays so

lib/isolate.cc

Index: lib/isolate.cc
===================================================================
--- lib/isolate.cc	(revision 16288)
+++ lib/isolate.cc	(working copy)
@@ -149,15 +149,15 @@
 
 
 static void ThrowIllegalArgException(const String& message) {
-  GrowableArray<const Object*> args(1);
-  args.Add(&message);
+  const Array& args = Array::Handle(Array::New(1));
+  args.SetAt(0, message);
   Exceptions::ThrowByType(Exceptions::kArgument, args);
 }
 
 
 static void ThrowIsolateSpawnException(const String& message) {
-  GrowableArray<const Object*> args(1);
-  args.Add(&message);
+  const Array& args = Array::Handle(Array::New(1));
+  args.SetAt(0, message);
   Exceptions::ThrowByType(Exceptions::kIsolateSpawn, args);
 }