Fixes a couple problems with GC of unoptimized code.

runtime/vm/megamorphic_cache_table.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/megamorphic_cache_table.h"
 
 #include <stdlib.h>
 #include "vm/object.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
 
 namespace dart {
 
 MegamorphicCacheTable::MegamorphicCacheTable()
-    : miss_handler_(NULL),
+    : miss_handler_function_(NULL),
+      miss_handler_code_(NULL),
       capacity_(0),
       length_(0),
       table_(NULL) {
 }
 
 
 MegamorphicCacheTable::~MegamorphicCacheTable() {
   free(table_);
 }
 
@@ skipping 32 matching lines @@
       Class::Handle(Type::Handle(Type::Function()).type_class());
   const Function& function =
       Function::Handle(Function::New(Symbols::MegamorphicMiss(),
                                      RawFunction::kRegularFunction,
                                      false,  // Not static.
                                      false,  // Not const.
                                      false,  // Not abstract.
                                      false,  // Not external.
                                      cls,
                                      0));  // No token position.
+  miss_handler_code_ = code.raw();
+  miss_handler_function_ = function.raw();
   function.SetCode(code);
-  miss_handler_ = function.raw();
 }
 
 
 void MegamorphicCacheTable::VisitObjectPointers(ObjectPointerVisitor* v) {
   ASSERT(v != NULL);
-  v->VisitPointer(reinterpret_cast<RawObject**>(&miss_handler_));
+  v->VisitPointer(reinterpret_cast<RawObject**>(&miss_handler_code_));
+  v->VisitPointer(reinterpret_cast<RawObject**>(&miss_handler_function_));
   for (intptr_t i = 0; i < length_; ++i) {
     v->VisitPointer(reinterpret_cast<RawObject**>(&table_[i].name));
     v->VisitPointer(reinterpret_cast<RawObject**>(&table_[i].descriptor));
     v->VisitPointer(reinterpret_cast<RawObject**>(&table_[i].cache));
   }
 }
 
 
 void MegamorphicCacheTable::PrintSizes() {
   StackZone zone(Isolate::Current());
   intptr_t size = 0;
   MegamorphicCache& cache = MegamorphicCache::Handle();
   Array& buckets = Array::Handle();
   for (intptr_t i = 0; i < length_; ++i) {
     cache = table_[i].cache;
     buckets = cache.buckets();
     size += MegamorphicCache::InstanceSize();
     size += Array::InstanceSize(buckets.Length());
   }
   OS::Print("%" Pd " megamorphic caches using %" Pd "KB.\n",
             length_, size / 1024);
 }
 
 }  // namespace dart