Remove vestigial legacy const handling from parser

src/parsing/pattern-rewriter.cc

 // Copyright 2015 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/ast/ast.h"
 #include "src/messages.h"
 #include "src/parsing/parameter-initializer-rewriter.h"
 #include "src/parsing/parser.h"
 
 namespace v8 {
@@ skipping 254 matching lines @@
       } else {
         initialize = NULL;
       }
     }
 
     if (initialize != NULL) {
       block_->statements()->Add(
           factory()->NewExpressionStatement(initialize, initialize->position()),
           zone());
     }
-  } else if (value != nullptr && (descriptor_->mode == CONST_LEGACY ||
-                                  IsLexicalVariableMode(descriptor_->mode))) {
-    // Constant initializations always assign to the declared constant which
-    // is always at the function scope level. This is only relevant for
-    // dynamically looked-up variables and constants (the
-    // start context for constant lookups is always the function context,
-    // while it is the top context for var declared variables). Sigh...
-    // For 'let' and 'const' declared variables in harmony mode the
-    // initialization also always assigns to the declared variable.
+  } else if (value != nullptr && IsLexicalVariableMode(descriptor_->mode)) {
+    // For 'let' and 'const' declared variables the initialization always
+    // assigns to the declared variable.
     DCHECK_NOT_NULL(proxy);
     DCHECK_NOT_NULL(proxy->var());
     DCHECK_NOT_NULL(value);
     // Add break location for destructured sub-pattern.
     int pos = IsSubPattern() ? pattern->position() : value->position();
     Assignment* assignment =
         factory()->NewAssignment(Token::INIT, proxy, value, pos);
     block_->statements()->Add(
         factory()->NewExpressionStatement(assignment, pos), zone());
     value = NULL;
@@ skipping 452 matching lines @@
 NOT_A_PATTERN(TryFinallyStatement)
 NOT_A_PATTERN(UnaryOperation)
 NOT_A_PATTERN(VariableDeclaration)
 NOT_A_PATTERN(WhileStatement)
 NOT_A_PATTERN(WithStatement)
 NOT_A_PATTERN(Yield)
 
 #undef NOT_A_PATTERN
 }  // namespace internal
 }  // namespace v8