Implement proper scoping for "this" in arrow functions

src/x87/lithium-codegen-x87.cc

Index: src/x87/lithium-codegen-x87.cc
diff --git a/src/x87/lithium-codegen-x87.cc b/src/x87/lithium-codegen-x87.cc
index c9c8a47593200a01ef005ad6c52bac8e37aa1f6c..a9eda28f80ebd80d63961c027e9c431a57a0915d 100644
--- a/src/x87/lithium-codegen-x87.cc
+++ b/src/x87/lithium-codegen-x87.cc
@@ -111,7 +111,8 @@ bool LCodeGen::GeneratePrologue() {
     // object).
     if (info_->this_has_uses() &&
         info_->strict_mode() == SLOPPY &&
-        !info_->is_native()) {
+        !info_->is_native() &&
+        info_->scope->has_this_declaration()) {
       Label ok;
       // +1 for return address.
       int receiver_offset = (scope()->num_parameters() + 1) * kPointerSize;
@@ -241,8 +242,9 @@ bool LCodeGen::GeneratePrologue() {
 
     // Copy parameters into context if necessary.
     int num_parameters = scope()->num_parameters();
-    for (int i = 0; i < num_parameters; i++) {
-      Variable* var = scope()->parameter(i);
+    int first_parameter = scope()->has_this_declaration() ? -1 : 0;
+    for (int i = first_parameter; i < num_parameters; i++) {
+      Variable* var = (i == -1) ? scope()->receiver() : scope()->parameter(i);
       if (var->IsContextSlot()) {
         int parameter_offset = StandardFrameConstants::kCallerSPOffset +
             (num_parameters - 1 - i) * kPointerSize;