add interceptors which do not mask existing properties

src/ic/handler-compiler.cc

Index: src/ic/handler-compiler.cc
diff --git a/src/ic/handler-compiler.cc b/src/ic/handler-compiler.cc
index 15dc941503e8309798b78ea47f2ba01ec2fa8465..8752c6cfced1097a05a976fb521f6ce49037baa9 100644
--- a/src/ic/handler-compiler.cc
+++ b/src/ic/handler-compiler.cc
@@ -311,7 +311,25 @@ Handle<Code> NamedLoadHandlerCompiler::CompileLoadInterceptor(
 
   Label miss;
   InterceptorVectorSlotPush(receiver());
+  auto holder_orig = holder();
+  // Temporarily swap holder to check entire chain.  What could go wrong?
+  if (holder()->GetNamedInterceptor()->non_masking()) {
+    DCHECK(!inline_followup);
+    JSObject* last = *holder();
+    PrototypeIterator iter(isolate(), last);
+    while (!iter.IsAtEnd()) {
+      last = JSObject::cast(iter.GetCurrent());
+      iter.Advance();
+    }
+    auto last_handle = handle(last);
+    set_holder(last_handle);
+  }
   Register reg = FrontendHeader(receiver(), it->name(), &miss);
+  // Now do the check again, getting the holder into the right register...
+  if (holder_orig->GetNamedInterceptor()->non_masking()) {
+    set_holder(holder_orig);
+    reg = FrontendHeader(receiver(), it->name(), &miss);
+  }
   FrontendFooter(it->name(), &miss);
   InterceptorVectorSlotPop(reg);
 
@@ -320,6 +338,7 @@ Handle<Code> NamedLoadHandlerCompiler::CompileLoadInterceptor(
     // prototypes and ultimate answer.
     GenerateLoadInterceptorWithFollowup(it, reg);
   } else {
+    // TODO(dcarney): add a function for calling nonmasking interceptors.
     GenerateLoadInterceptor(reg);
   }
   return GetCode(kind(), Code::FAST, it->name());