Disable reg-exp compilation in background via a flag

runtime/vm/flow_graph_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/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/branch_optimizer.h"
 #include "vm/cha.h"
 #include "vm/compiler.h"
@@ skipping 4625 matching lines @@
     if (!getter.IsNull() && !setter.IsNull()) {
       if (field.is_double_initialized()) {
         unboxed_field = true;
       } else if ((setter.usage_counter() > 0) &&
                  ((FLAG_getter_setter_ratio * setter.usage_counter()) >=
                    getter.usage_counter())) {
         unboxed_field = true;
       }
     }
     if (!unboxed_field) {
+      // TODO(srdjan): Instead of aborting pass this field to the mutator thread
+      // so that it can:
+      // - set it to unboxed
+      // - deoptimize dependent code.
+      if (Compiler::IsBackgroundCompilation()) {
+        Compiler::AbortBackgroundCompilation(Thread::kNoDeoptId);
+      }
       if (FLAG_trace_optimization || FLAG_trace_field_guards) {
         THR_Print("Disabling unboxing of %s\n", field.ToCString());
         if (!setter.IsNull()) {
           OS::Print("  setter usage count: %" Pd "\n", setter.usage_counter());
         }
         if (!getter.IsNull()) {
           OS::Print("  getter usage count: %" Pd "\n", getter.usage_counter());
         }
       }
       field.set_is_unboxing_candidate(false);
       if (Compiler::IsBackgroundCompilation()) {
-        // Delay deoptimization of dependent code to the code installation time.
-        // The invalidation of the background compilation result occurs only
-        // when the deoptimization is triggered at code installation.
-        flow_graph()->deoptimize_dependent_code().Add(&field);
+        UNIMPLEMENTED();
       } else {
         field.DeoptimizeDependentCode();
       }
     } else {
       FlowGraph::AddToGuardedFields(flow_graph_->guarded_fields(), &field);
     }
   }
 }
 
 
@@ skipping 378 matching lines @@
         // the code for this instruction, however, leaving the environment
         // changes code.
         current->RemoveEnvironment();
       }
     }
   }
 }
 
 
 }  // namespace dart