[Object.observe] Don't force normalization of elements for observed objects

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
diff --git a/src/x64/stub-cache-x64.cc b/src/x64/stub-cache-x64.cc
index 499ccdf24caeadb9b648cf5a846633241de815e6..03c4e73ff89a64933ba2896fd339bfe72d87c3fd 100644
--- a/src/x64/stub-cache-x64.cc
+++ b/src/x64/stub-cache-x64.cc
@@ -1661,8 +1661,12 @@ Handle<Code> CallStubCompiler::CompileArrayPushCall(
   //  -- rsp[(argc + 1) * 8] : receiver
   // -----------------------------------
 
-  // If object is not an array, bail out to regular call.
-  if (!object->IsJSArray() || !cell.is_null()) return Handle<Code>::null();
+  // If object is not an array or is observed, bail out to regular call.
+  if (!object->IsJSArray() ||
+      !cell.is_null() ||
+      Handle<JSArray>::cast(object)->map()->is_observed()) {
+    return Handle<Code>::null();
+  }
 
   Label miss;
   GenerateNameCheck(name, &miss);
@@ -1912,8 +1916,12 @@ Handle<Code> CallStubCompiler::CompileArrayPopCall(
   //  -- rsp[(argc + 1) * 8] : receiver
   // -----------------------------------
 
-  // If object is not an array, bail out to regular call.
-  if (!object->IsJSArray() || !cell.is_null()) return Handle<Code>::null();
+  // If object is not an array or is observed, bail out to regular call.
+  if (!object->IsJSArray() ||
+      !cell.is_null() ||
+      Handle<JSArray>::cast(object)->map()->is_observed()) {
+    return Handle<Code>::null();
+  }
 
   Label miss, return_undefined, call_builtin;
   GenerateNameCheck(name, &miss);