Add script context with context-allocated "const this"

src/variables.h

 // Copyright 2011 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_VARIABLES_H_
 #define V8_VARIABLES_H_
 
 #include "src/ast-value-factory.h"
 #include "src/zone.h"
 
@@ skipping 87 matching lines @@
   bool is_const_mode() const { return IsImmutableVariableMode(mode_); }
   bool binding_needs_init() const {
     return initialization_flag_ == kNeedsInitialization;
   }
 
   bool is_function() const { return kind_ == FUNCTION; }
   bool is_class() const { return kind_ == CLASS; }
   bool is_this() const { return kind_ == THIS; }
   bool is_arguments() const { return kind_ == ARGUMENTS; }
 
+  // For script scopes, the "this" binding is provided by a ScriptContext added
+  // to the global's ScriptContextTable.  This binding might not statically
+  // resolve to a Variable::THIS binding, instead being DYNAMIC_LOCAL.  However
+  // any variable named "this" does indeed refer to a Variable::THIS binding;
+  // the grammar ensures this to be the case.  So wherever a "this" binding
+  // might be provided by the global, use HasThisName instead of is_this().
+  bool HasThisName(Isolate* isolate) const {
+    return is_this() || *name() == *isolate->factory()->this_string();
+  }
+
   ClassVariable* AsClassVariable() {
     DCHECK(is_class());
     return reinterpret_cast<ClassVariable*>(this);
   }
 
   // True if the variable is named eval and not known to be shadowed.
   bool is_possibly_eval(Isolate* isolate) const {
     return IsVariable(isolate->factory()->eval_string());
   }
 
@@ skipping 82 matching lines @@
 
  private:
   // For classes we keep track of consecutive groups of delcarations. They are
   // needed for strong mode scoping checks. TODO(marja, rossberg): Implement
   // checks for functions too.
   int declaration_group_start_;
 };
 } }  // namespace v8::internal
 
 #endif  // V8_VARIABLES_H_