Fixes a couple problems with GC of unoptimized code.

runtime/vm/raw_object.h

 // 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.
 
 #ifndef VM_RAW_OBJECT_H_
 #define VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/globals.h"
 #include "vm/token.h"
@@ skipping 592 matching lines @@
     kImplicitSetter,     // represents an implicit setter for fields.
     kImplicitStaticFinalGetter,  // represents an implicit getter for static
                                  // final fields (incl. static const fields).
     kStaticInitializer,  // used in implicit static getters.
     kMethodExtractor,  // converts method into implicit closure on the receiver.
     kNoSuchMethodDispatcher,  // invokes noSuchMethod.
     kInvokeFieldDispatcher,  // invokes a field as a closure.
   };
 
  private:
+  // So that the MarkingVisitor::DetachCode can null out the code fields.
+  friend class MarkingVisitor;
   friend class Class;
   RAW_HEAP_OBJECT_IMPLEMENTATION(Function);
+  static bool SkipCode(RawFunction* raw_fun);
 
   RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->name_); }
   RawString* name_;
   RawObject* owner_;  // Class or patch class or mixin class
                       // where this function is defined.
   RawAbstractType* result_type_;
   RawArray* parameter_types_;
   RawArray* parameter_names_;
+  RawObject* data_;  // Additional data specific to the function kind.
   RawCode* code_;  // Compiled code for the function.
   RawCode* unoptimized_code_;  // Unoptimized code, keep it after optimization.
-  RawObject* data_;  // Additional data specific to the function kind.
   RawObject** to() {
+    return reinterpret_cast<RawObject**>(&ptr()->unoptimized_code_);
+  }
+  RawObject** to_no_code() {
     return reinterpret_cast<RawObject**>(&ptr()->data_);
   }
 
   intptr_t token_pos_;
   intptr_t end_token_pos_;
   intptr_t usage_counter_;  // Incremented while function is running.
   int16_t num_fixed_parameters_;
   int16_t num_optional_parameters_;  // > 0: positional; < 0: named.
   int16_t deoptimization_counter_;
   uint16_t kind_tag_;  // See Function::KindTagBits.
@@ skipping 1088 matching lines @@
   // Make sure this is updated when new TypedData types are added.
   ASSERT(kTypedDataInt8ArrayViewCid == kTypedDataInt8ArrayCid + 13);
   ASSERT(kExternalTypedDataInt8ArrayCid == kTypedDataInt8ArrayViewCid + 14);
   ASSERT(kNullCid == kExternalTypedDataInt8ArrayCid + 13);
   return (kNullCid - kTypedDataInt8ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_