Pass handles not raw objects into methods.

runtime/vm/dart_entry.h

Index: runtime/vm/dart_entry.h
===================================================================
--- runtime/vm/dart_entry.h	(revision 15741)
+++ runtime/vm/dart_entry.h	(working copy)
@@ -22,6 +22,7 @@
 class RawArray;
 class RawInstance;
 class RawObject;
+class RawString;
 class String;
 
 // An arguments descriptor array consists of the total argument count; the
@@ -30,13 +31,13 @@
 // simplify iterating in generated code.
 class ArgumentsDescriptor : public ValueObject {
  public:
-  explicit ArgumentsDescriptor(RawObject* array);
+  explicit ArgumentsDescriptor(const Array& array);
 
   // Accessors.
   intptr_t Count() const;
   intptr_t PositionalCount() const;
   intptr_t NamedCount() const { return Count() - PositionalCount(); }
-  RawObject* NameAt(intptr_t index) const;
+  RawString* NameAt(intptr_t index) const;
 
   // Generated code support.
   static intptr_t count_offset();
@@ -73,6 +74,8 @@
   }
 
   const Array& array_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArgumentsDescriptor);
 };