Remember deopt-id -> context-level mappings in var descriptors.

runtime/vm/flow_graph_inliner.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.
 #if !defined(DART_PRECOMPILED_RUNTIME)
 #include "vm/flow_graph_inliner.h"
 
 #include "vm/aot_optimizer.h"
 #include "vm/precompiler.h"
 #include "vm/block_scheduler.h"
 #include "vm/branch_optimizer.h"
@@ skipping 782 matching lines @@
 
         // Build the callee graph.
         InlineExitCollector* exit_collector =
             new (Z) InlineExitCollector(caller_graph_, call);
         FlowGraph* callee_graph;
         if (UseKernelFrontEndFor(parsed_function)) {
           kernel::TreeNode* node = static_cast<kernel::TreeNode*>(
               parsed_function->function().kernel_function());
 
           kernel::FlowGraphBuilder builder(
-              node, parsed_function, *ic_data_array, exit_collector,
+              node, parsed_function, *ic_data_array,
+              /* not building var desc */ NULL, exit_collector,
               Compiler::kNoOSRDeoptId, caller_graph_->max_block_id() + 1);
           {
             CSTAT_TIMER_SCOPE(thread(), graphinliner_build_timer);
             callee_graph = builder.BuildGraph();
           }
         } else {
           FlowGraphBuilder builder(*parsed_function, *ic_data_array,
+                                   /* not building var desc */ NULL,
                                    exit_collector, Compiler::kNoOSRDeoptId);
           builder.SetInitialBlockId(caller_graph_->max_block_id());
           {
             CSTAT_TIMER_SCOPE(thread(), graphinliner_build_timer);
             callee_graph = builder.BuildGraph();
           }
         }
 #ifdef DART_PRECOMPILER
         if (FLAG_precompiled_mode) {
           Precompiler::PopulateWithICData(parsed_function->function(),
@@ skipping 2947 matching lines @@
     }
 
     default:
       return false;
   }
 }
 
 
 }  // namespace dart
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)