Remove vestigial legacy const handling from parser

src/parsing/parser.cc

Index: src/parsing/parser.cc
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index 3751acba6bd4be2c24628625f2fd5c29765c2b53..53d18fb3e9b9304d1def1dfcd04806924f298231 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -1972,14 +1972,6 @@ Variable* Parser::Declare(Declaration* declaration,
   // RuntimeHidden_DeclareLookupSlot calls.
   declaration_scope->AddDeclaration(declaration);
 
-  if (mode == CONST_LEGACY && declaration_scope->is_script_scope()) {
-    // For global const variables we bind the proxy to a variable.
-    DCHECK(resolve);  // should be set by all callers
-    Variable::Kind kind = Variable::NORMAL;
-    var = new (zone()) Variable(declaration_scope, name, mode, kind,
-                                kNeedsInitialization, kNotAssigned);
-  }
-
   // If requested and we have a local variable, bind the proxy to the variable
   // at parse-time. This is used for functions (and consts) declared inside
   // statements: the corresponding function (or const) variable must be in the
@@ -2344,9 +2336,8 @@ Block* Parser::ParseVariableDeclarations(
           return nullptr;
         }
 
-        // 'let x' and (legacy) 'const x' initialize 'x' to undefined.
-        if (parsing_result->descriptor.mode == LET ||
-            parsing_result->descriptor.mode == CONST_LEGACY) {
+        // 'let x' initializes 'x' to undefined.
+        if (parsing_result->descriptor.mode == LET) {
           value = GetLiteralUndefined(position());
         }
       }