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

runtime/vm/kernel_to_il.h

 // Copyright (c) 2016, 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_KERNEL_TO_IL_H_
 #define RUNTIME_VM_KERNEL_TO_IL_H_
 
 #if !defined(DART_PRECOMPILED_RUNTIME)
 
 #include "vm/growable_array.h"
@@ skipping 768 matching lines @@
 
   YieldContinuation()
       : entry(NULL), try_index(CatchClauseNode::kInvalidTryIndex) {}
 };
 
 class FlowGraphBuilder : public ExpressionVisitor, public StatementVisitor {
  public:
   FlowGraphBuilder(TreeNode* node,
                    ParsedFunction* parsed_function,
                    const ZoneGrowableArray<const ICData*>& ic_data_array,
+                   ZoneGrowableArray<intptr_t>* context_level_array,
                    InlineExitCollector* exit_collector,
                    intptr_t osr_id,
                    intptr_t first_block_id = 1);
   virtual ~FlowGraphBuilder();
 
   FlowGraph* BuildGraph();
 
   virtual void VisitDefaultExpression(Expression* node) { UNREACHABLE(); }
   virtual void VisitDefaultStatement(Statement* node) { UNREACHABLE(); }
 
@@ skipping 246 matching lines @@
   Thread* thread_;
   Zone* zone_;
 
   // The node we are currently compiling (e.g. FunctionNode, Constructor,
   // Field)
   TreeNode* node_;
 
   ParsedFunction* parsed_function_;
   intptr_t osr_id_;
   const ZoneGrowableArray<const ICData*>& ic_data_array_;
+  // Contains (deopt_id, context_level) pairs.
+  ZoneGrowableArray<intptr_t>* context_level_array_;
   InlineExitCollector* exit_collector_;
 
   intptr_t next_block_id_;
   intptr_t AllocateBlockId() { return next_block_id_++; }
 
   intptr_t GetNextDeoptId() {
-    // TODO(rmacnak): Record current scope / context level.
-    return thread_->GetNextDeoptId();
+    intptr_t deopt_id = thread_->GetNextDeoptId();
+    if (context_level_array_ != NULL) {
+      intptr_t level = context_depth_;
+      context_level_array_->Add(deopt_id);
+      context_level_array_->Add(level);
+    }
+    return deopt_id;
   }
 
   intptr_t next_function_id_;
   intptr_t AllocateFunctionId() { return next_function_id_++; }
 
   intptr_t context_depth_;
   intptr_t loop_depth_;
   intptr_t try_depth_;
   intptr_t catch_depth_;
   intptr_t for_in_depth_;
@@ skipping 294 matching lines @@
 namespace kernel {
 
 RawObject* EvaluateMetadata(const dart::Field& metadata_field);
 RawObject* BuildParameterDescriptor(const Function& function);
 
 }  // namespace kernel
 }  // namespace dart
 
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)
 #endif  // RUNTIME_VM_KERNEL_TO_IL_H_