Add support for calculating a scopes maximum nested context chain.

src/scopes.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/scopes.h"
 
 #include "src/accessors.h"
 #include "src/bootstrapper.h"
 #include "src/messages.h"
 #include "src/parser.h"
@@ skipping 747 matching lines @@
 
 bool Scope::AllowsLazyCompilationWithoutContext() const {
   return !force_eager_compilation_ && HasTrivialOuterContext();
 }
 
 
 int Scope::ContextChainLength(Scope* scope) {
   int n = 0;
   for (Scope* s = this; s != scope; s = s->outer_scope_) {
     DCHECK(s != NULL);  // scope must be in the scope chain
-    if (s->is_with_scope() || s->num_heap_slots() > 0) n++;
-    // Catch and module scopes always have heap slots.
-    DCHECK(!s->is_catch_scope() || s->num_heap_slots() > 0);
-    DCHECK(!s->is_module_scope() || s->num_heap_slots() > 0);
+    if (s->NeedsContext()) n++;
   }
   return n;
 }
 
 
+int Scope::MaxNestedContextChainLength() {
+  int max_context_chain_length = 0;
+  for (int i = 0; i < inner_scopes_.length(); i++) {
+    Scope* scope = inner_scopes_[i];
+    max_context_chain_length = std::max(scope->MaxNestedContextChainLength(),
+                                        max_context_chain_length);
+  }
+  if (NeedsContext()) {
+    max_context_chain_length += 1;
+  }
+  return max_context_chain_length;
+}
+
+
 Scope* Scope::DeclarationScope() {
   Scope* scope = this;
   while (!scope->is_declaration_scope()) {
     scope = scope->outer_scope();
   }
   return scope;
 }
 
 
 Scope* Scope::ClosureScope() {
@@ skipping 860 matching lines @@
       function_ != NULL && function_->proxy()->var()->IsContextSlot();
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS - num_global_slots() -
          (is_function_var_in_context ? 1 : 0);
 }
 
 
 int Scope::ContextGlobalCount() const { return num_global_slots(); }
 
 }  // namespace internal
 }  // namespace v8