Remove redundant variable descriptors from optimized code.

runtime/vm/flow_graph_compiler.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/globals.h"  // Needed here to get TARGET_ARCH_XXX.
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
@@ skipping 870 matching lines @@
     code.set_stackmaps(Object::null_array());
   } else {
     // Finalize the stack map array and add it to the code object.
     code.set_stackmaps(
         Array::Handle(stackmap_table_builder_->FinalizeStackmaps(code)));
   }
 }
 
 
 void FlowGraphCompiler::FinalizeVarDescriptors(const Code& code) {
+  if (code.is_optimized()) {
+    // Optimized code does not need variable descriptors. They are
+    // only stored in the unoptimized version.
+    code.set_var_descriptors(Object::empty_var_descriptors());
+    return;
+  }
   LocalVarDescriptors& var_descs = LocalVarDescriptors::Handle();
   if (parsed_function().node_sequence() == NULL) {
     ASSERT(flow_graph().IsIrregexpFunction());
     var_descs = LocalVarDescriptors::New(1);
     RawLocalVarDescriptors::VarInfo info;
     info.set_kind(RawLocalVarDescriptors::kSavedCurrentContext);
     info.scope_id = 0;
     info.begin_pos = 0;
     info.end_pos = 0;
     info.set_index(parsed_function().current_context_var()->index());
@@ skipping 773 matching lines @@
 
 
 void FlowGraphCompiler::FrameStateClear() {
   ASSERT(!is_optimizing());
   frame_state_.TruncateTo(0);
 }
 #endif
 
 
 }  // namespace dart