Use VM type cast and save handles.

runtime/vm/debugger.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/debugger.h"
 
 #include "vm/code_generator.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
@@ skipping 637 matching lines @@
   return (src_breakpoints_ != NULL) ||
          (code_breakpoints_ != NULL) ||
          (exc_pause_info_ != kNoPauseOnExceptions);
 }
 
 
 static RawFunction* ResolveLibraryFunction(
                         const Library& library,
                         const String& fname) {
   ASSERT(!library.IsNull());
-  Function& function = Function::Handle();
   const Object& object = Object::Handle(library.LookupObject(fname));
   if (!object.IsNull() && object.IsFunction()) {
-    function ^= object.raw();
+    return Function::Cast(object).raw();
   }
-  return function.raw();
+  return Function::null();
 }
 
 
 RawFunction* Debugger::ResolveFunction(const Library& library,
                                        const String& class_name,
                                        const String& function_name) {
   ASSERT(!library.IsNull());
   ASSERT(!class_name.IsNull());
   ASSERT(!function_name.IsNull());
   if (class_name.Length() == 0) {
@@ skipping 879 matching lines @@
 }
 
 
 void Debugger::RegisterCodeBreakpoint(CodeBreakpoint* bpt) {
   ASSERT(bpt->next() == NULL);
   bpt->set_next(code_breakpoints_);
   code_breakpoints_ = bpt;
 }
 
 }  // namespace dart