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

runtime/vm/intermediate_language.h

 // 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.
 
 #ifndef RUNTIME_VM_INTERMEDIATE_LANGUAGE_H_
 #define RUNTIME_VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 915 matching lines @@
   void Unsupported(FlowGraphCompiler* compiler);
 
  protected:
   // GetDeoptId and/or CopyDeoptIdFrom.
   friend class CallSiteInliner;
   friend class LICM;
   friend class ComparisonInstr;
   friend class Scheduler;
   friend class BlockEntryInstr;
   friend class CatchBlockEntryInstr;  // deopt_id_
+  friend class DebugStepCheckInstr;   // deopt_id_
+  friend class StrictCompareInstr;    // deopt_id_
 
   // Fetch deopt id without checking if this computation can deoptimize.
   intptr_t GetDeoptId() const { return deopt_id_; }
 
   void CopyDeoptIdFrom(const Instruction& instr) {
     deopt_id_ = instr.deopt_id_;
   }
 
  private:
   friend class BranchInstr;      // For RawSetInputAt.
@@ skipping 2675 matching lines @@
   bool is_auto_scope_;
   bool link_lazily_;
   const TokenPosition token_pos_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeCallInstr);
 };
 
 
 class DebugStepCheckInstr : public TemplateInstruction<0, NoThrow> {
  public:
-  DebugStepCheckInstr(TokenPosition token_pos, RawPcDescriptors::Kind stub_kind)
-      : token_pos_(token_pos), stub_kind_(stub_kind) {}
+  DebugStepCheckInstr(TokenPosition token_pos,
+                      RawPcDescriptors::Kind stub_kind,
+                      intptr_t deopt_id)
+      : TemplateInstruction<0, NoThrow>(deopt_id),
+        token_pos_(token_pos),
+        stub_kind_(stub_kind) {}
 
   DECLARE_INSTRUCTION(DebugStepCheck)
 
   virtual TokenPosition token_pos() const { return token_pos_; }
   virtual bool ComputeCanDeoptimize() const { return false; }
   virtual EffectSet Effects() const { return EffectSet::All(); }
   virtual Instruction* Canonicalize(FlowGraph* flow_graph);
 
  private:
   const TokenPosition token_pos_;
@@ skipping 4586 matching lines @@
   LocationSummary* Name::MakeLocationSummary(Zone* zone, bool opt) const {     \
     UNIMPLEMENTED();                                                           \
     return NULL;                                                               \
   }                                                                            \
   void Name::EmitNativeCode(FlowGraphCompiler* compiler) { UNIMPLEMENTED(); }
 
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_INTERMEDIATE_LANGUAGE_H_