More fixes for background compilation

runtime/vm/jit_optimizer.cc

 // Copyright (c) 2013, 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/jit_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/branch_optimizer.h"
 #include "vm/cha.h"
 #include "vm/compiler.h"
@@ skipping 1244 matching lines @@
         Token::kNEGATE, new(Z) Value(input), call->deopt_id());
   } else {
     return false;
   }
   ASSERT(unary_op != NULL);
   ReplaceCall(call, unary_op);
   return true;
 }
 
 
-// Using field class
+// Using field class.
 RawField* JitOptimizer::GetField(intptr_t class_id,
                                  const String& field_name) {
   Class& cls = Class::Handle(Z, isolate()->class_table()->At(class_id));
   Field& field = Field::Handle(Z);
   while (!cls.IsNull()) {
     field = cls.LookupInstanceField(field_name);
     if (!field.IsNull()) {
-      return field.raw();
+      if (Compiler::IsBackgroundCompilation() ||
+          FLAG_force_clone_compiler_objects) {
+        return field.CloneFromOriginal();
+      } else {
+        return field.raw();
+      }
     }
     cls = cls.SuperClass();
   }
   return Field::null();
 }
 
 
 // Use CHA to determine if the call needs a class check: if the callee's
 // receiver is the same as the caller's receiver and there are no overriden
 // callee functions, then no class check is needed.
@@ skipping 1864 matching lines @@
 
   // Discard the environment from the original instruction because the store
   // can't deoptimize.
   instr->RemoveEnvironment();
   ReplaceCall(instr, store);
   return true;
 }
 
 
 }  // namespace dart