Implement proper scoping for "this" in arrow functions

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index 3a93117e385542c259016c087242a171bed3c289..b2c8328d96c53e0aee922fe0ddaa8beb17a0f75b 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -114,7 +114,8 @@ void FullCodeGenerator::Generate() {
   // Sloppy mode functions and builtins need to replace the receiver with the
   // global proxy when called as functions (without an explicit receiver
   // object).
-  if (info->strict_mode() == SLOPPY && !info->is_native()) {
+  if (info->strict_mode() == SLOPPY && !info->is_native() &&
+      info->scope()->has_this_declaration()) {
     Label ok;
     // +1 for return address.
     StackArgumentsAccessor args(rsp, info->scope()->num_parameters());
@@ -208,8 +209,9 @@ void FullCodeGenerator::Generate() {
 
     // Copy any necessary parameters into the context.
     int num_parameters = info->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;