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

src/arm/stub-cache-arm.cc

Index: src/arm/stub-cache-arm.cc
diff --git a/src/arm/stub-cache-arm.cc b/src/arm/stub-cache-arm.cc
index a7ddc8e5326c57aec534ee51d64b8d26d60fd111..23fe0930a34c745e7ee4e042f96bb6cc40b69786 100644
--- a/src/arm/stub-cache-arm.cc
+++ b/src/arm/stub-cache-arm.cc
@@ -1718,8 +1718,12 @@ Handle<Code> CallStubCompiler::CompileArrayPushCall(
   //  -- sp[argc * 4]           : 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);
@@ -1972,8 +1976,12 @@ Handle<Code> CallStubCompiler::CompileArrayPopCall(
   //  -- sp[argc * 4]           : 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;
   Register receiver = r1;