[Interpreter] Adds support for const/let variables to interpreter.

src/interpreter/bytecode-generator.h

Index: src/interpreter/bytecode-generator.h
diff --git a/src/interpreter/bytecode-generator.h b/src/interpreter/bytecode-generator.h
index be4ca82e36409268f9f041bcf9aa755c7517bc71..d1ff0dca462b53afcc5e0d789874deb0b503698b 100644
--- a/src/interpreter/bytecode-generator.h
+++ b/src/interpreter/bytecode-generator.h
@@ -74,7 +74,13 @@ class BytecodeGenerator final : public AstVisitor {
   MUST_USE_RESULT Register
   VisitVariableLoadForRegisterValue(Variable* variable, FeedbackVectorSlot slot,
                                     TypeofMode typeof_mode = NOT_INSIDE_TYPEOF);
-  void VisitVariableAssignment(Variable* variable, FeedbackVectorSlot slot);
+  void VisitVariableAssignment(Variable* variable, Token::Value op,
+                               FeedbackVectorSlot slot);
+  void BuildThrowIfHole(Handle<String> name);
+  void BuildThrowIfNotHole(Handle<String> name);
+  void BuildThrowReassignConstant(Handle<String> name);
+  void BuildHoleCheckForVariableLoad(VariableMode mode, Handle<String> name);
+  void BuildHoleCheckForVariableAssignment(Variable* variable, Token::Value op);
 
   void VisitArgumentsObject(Variable* variable);
   void VisitRestArgumentsArray(Variable* rest, int index);