Do not look for the slot in the ScopeInfo's global range when it's not necessary.

src/objects.h

 // 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.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 3880 matching lines @@
   String* StrongModeFreeVariableName(int var);
   int StrongModeFreeVariableStartPosition(int var);
   int StrongModeFreeVariableEndPosition(int var);
 
   // Lookup support for serialized scope info. Returns the
   // the stack slot index for a given slot name if the slot is
   // present; otherwise returns a value < 0. The name must be an internalized
   // string.
   int StackSlotIndex(String* name);
 
-  // Lookup support for serialized scope info. Returns the
-  // context slot index for a given slot name if the slot is present; otherwise
+  // Lookup support for serialized scope info. Returns the local context slot
+  // index for a given slot name if the slot is present; otherwise
   // returns a value < 0. The name must be an internalized string.
   // If the slot is present and mode != NULL, sets *mode to the corresponding
   // mode for that variable.
   static int ContextSlotIndex(Handle<ScopeInfo> scope_info, Handle<String> name,
-                              VariableMode* mode, VariableLocation* location,
-                              InitializationFlag* init_flag,
+                              VariableMode* mode, InitializationFlag* init_flag,
                               MaybeAssignedFlag* maybe_assigned_flag);
 
+  // Similar to ContextSlotIndex() but this method searches only among
+  // global slots of the serialized scope info. Returns the context slot index
+  // for a given slot name if the slot is present; otherwise returns a
+  // value < 0. The name must be an internalized string. If the slot is present
+  // and mode != NULL, sets *mode to the corresponding mode for that variable.
+  static int ContextGlobalSlotIndex(Handle<ScopeInfo> scope_info,
+                                    Handle<String> name, VariableMode* mode,
+                                    InitializationFlag* init_flag,
+                                    MaybeAssignedFlag* maybe_assigned_flag);
+
   // Lookup the name of a certain context slot by its index.
   String* ContextSlotName(int slot_index);
 
   // Lookup support for serialized scope info. Returns the
   // parameter index for a given parameter name if the parameter is present;
   // otherwise returns a value < 0. The name must be an internalized string.
   int ParameterIndex(String* name);
 
   // Lookup support for serialized scope info. Returns the function context
   // slot index if the function name is present and context-allocated (named
@@ skipping 6493 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_