Add flag to disable string externalization

runtime/vm/constant_propagator.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/constant_propagator.h"
 
 #include "vm/bit_vector.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/flow_graph_range_analysis.h"
@@ skipping 305 matching lines @@
   }
 }
 
 
 void ConstantPropagator::VisitRedefinition(RedefinitionInstr* instr) {
   // Ensure that we never remove redefinition of a constant unless we are also
   // are guaranteed to fold away code paths that correspond to non-matching
   // class ids. Otherwise LICM might potentially hoist incorrect code.
   const Object& value = instr->value()->definition()->constant_value();
   if (IsConstant(value) &&
-      CheckClassInstr::IsImmutableClassId(value.GetClassId())) {
+      !Field::IsExternalizableCid(value.GetClassId())) {
     SetValue(instr, value);
   } else {
     SetValue(instr, non_constant_);
   }
 }
 
 
 void ConstantPropagator::VisitParameter(ParameterInstr* instr) {
   SetValue(instr, non_constant_);
 }
@@ skipping 461 matching lines @@
 void ConstantPropagator::VisitLoadClassId(LoadClassIdInstr* instr) {
   intptr_t cid = instr->object()->Type()->ToCid();
   if (cid != kDynamicCid) {
     SetValue(instr, Smi::ZoneHandle(Z, Smi::New(cid)));
     return;
   }
 
   const Object& object = instr->object()->definition()->constant_value();
   if (IsConstant(object)) {
     cid = object.GetClassId();
-    if (CheckClassInstr::IsImmutableClassId(cid)) {
+    if (!Field::IsExternalizableCid(cid)) {
       SetValue(instr, Smi::ZoneHandle(Z, Smi::New(cid)));
       return;
     }
   }
   SetValue(instr, non_constant_);
 }
 
 
 void ConstantPropagator::VisitLoadField(LoadFieldInstr* instr) {
   Value* instance = instr->instance();
@@ skipping 866 matching lines @@
   graph_->MergeBlocks();
   GrowableArray<BitVector*> dominance_frontier;
   graph_->ComputeDominators(&dominance_frontier);
 
   if (FLAG_trace_constant_propagation) {
     FlowGraphPrinter::PrintGraph("After CP", graph_);
   }
 }
 
 }  // namespace dart