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

src/compiler/interpreter-assembler.h

Index: src/compiler/interpreter-assembler.h
diff --git a/src/compiler/interpreter-assembler.h b/src/compiler/interpreter-assembler.h
index ae5114da3b4519aa847c6648dcd91fc6823bd531..15e0e7ea471296b3baeae69ee2f3e609d8d1b6f0 100644
--- a/src/compiler/interpreter-assembler.h
+++ b/src/compiler/interpreter-assembler.h
@@ -146,9 +146,18 @@ class InterpreterAssembler {
   void Jump(Node* jump_offset);
 
   // Jump relative to the current bytecode by |jump_offset| if the
+  // |condition| is true. Helper function for JumpIfWordEqual and
+  // JumpIfWordNotEqual.
+  void JumpConditional(Node* condition, Node* jump_offset);
+
+  // Jump relative to the current bytecode by |jump_offset| if the
   // word values |lhs| and |rhs| are equal.
   void JumpIfWordEqual(Node* lhs, Node* rhs, Node* jump_offset);
 
+  // Jump relative to the current bytecode by |jump_offset| if the
+  // word values |lhs| and |rhs| are not equal.
+  void JumpIfWordNotEqual(Node* lhs, Node* rhs, Node* jump_offset);
+
   // Returns from the function.
   void Return();