[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 6fd09e537ba328e858f89d7bfa9d83ffb3167e84..f666171d89b21bf40fa278663a211b798043008d 100644
--- a/src/compiler/interpreter-assembler.h
+++ b/src/compiler/interpreter-assembler.h
@@ -148,9 +148,18 @@ 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);
+
   // Perform a stack guard check.
   void StackCheck();