Implement proper scoping for "this" in arrow functions

src/compiler/ast-graph-builder.h

Index: src/compiler/ast-graph-builder.h
diff --git a/src/compiler/ast-graph-builder.h b/src/compiler/ast-graph-builder.h
index aa874be5bdff7122b26fb78568d49b8536d6eaf3..4862525301d73a17c63c56852dfd9885ae33448b 100644
--- a/src/compiler/ast-graph-builder.h
+++ b/src/compiler/ast-graph-builder.h
@@ -348,21 +348,29 @@ class AstGraphBuilder::Environment : public ZoneObject {
   // Operations on parameter or local variables. The parameter indices are
   // shifted by 1 (receiver is parameter index -1 but environment index 0).
   void Bind(Variable* variable, Node* node) {
-    DCHECK(variable->IsStackAllocated());
-    if (variable->IsParameter()) {
-      values()->at(variable->index() + 1) = node;
+    if (variable->is_this()) {
+      values()->at(0) = node;
     } else {
-      DCHECK(variable->IsStackLocal());
-      values()->at(variable->index() + parameters_count_) = node;
+      DCHECK(variable->IsStackAllocated());
+      if (variable->IsParameter()) {
+        values()->at(variable->index() + 1) = node;
+      } else {
+        DCHECK(variable->IsStackLocal());
+        values()->at(variable->index() + parameters_count_) = node;
+      }
     }
   }
   Node* Lookup(Variable* variable) {
-    DCHECK(variable->IsStackAllocated());
-    if (variable->IsParameter()) {
-      return values()->at(variable->index() + 1);
+    if (variable->is_this()) {
+      return values()->at(0);
     } else {
-      DCHECK(variable->IsStackLocal());
-      return values()->at(variable->index() + parameters_count_);
+      DCHECK(variable->IsStackAllocated());
+      if (variable->IsParameter()) {
+        return values()->at(variable->index() + 1);
+      } else {
+        DCHECK(variable->IsStackLocal());
+        return values()->at(variable->index() + parameters_count_);
+      }
     }
   }