Create read only handles for empty_array and sentinel objects

vm/exceptions.cc

 // Copyright (c) 2011, 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/exceptions.h"
 
 #include "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
 #include "vm/flags.h"
@@ skipping 125 matching lines @@
       StubCode::JumpToErrorHandlerEntryPoint());
   func(program_counter, stack_pointer, frame_pointer, raw_error);
   UNREACHABLE();
 }
 
 
 static void ThrowExceptionHelper(const Instance& incoming_exception,
                                  const Instance& existing_stacktrace) {
   Instance& exception = Instance::Handle(incoming_exception.raw());
   if (exception.IsNull()) {
-    const Array& arguments = Array::Handle(Object::empty_array());
-    exception ^= Exceptions::Create(Exceptions::kNullThrown, arguments);
+    exception ^= Exceptions::Create(Exceptions::kNullThrown,
+                                    Object::empty_array());
   }
   uword handler_pc = 0;
   uword handler_sp = 0;
   uword handler_fp = 0;
   const GrowableObjectArray& func_list =
       GrowableObjectArray::Handle(GrowableObjectArray::New());
   const GrowableObjectArray& code_list =
       GrowableObjectArray::Handle(GrowableObjectArray::New());
   const GrowableObjectArray& pc_offset_list =
       GrowableObjectArray::Handle(GrowableObjectArray::New());
@@ skipping 283 matching lines @@
     case kIsolateUnhandledException:
       library = Library::IsolateLibrary();
       class_name = Symbols::New("IsolateUnhandledException");
       break;
   }
 
   return DartLibraryCalls::ExceptionCreate(library, class_name, arguments);
 }
 
 }  // namespace dart