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

src/mips/stub-cache-mips.cc

Index: src/mips/stub-cache-mips.cc
diff --git a/src/mips/stub-cache-mips.cc b/src/mips/stub-cache-mips.cc
index 27be2d45147836c34c4ad0b2d96fe89665d6f8dc..d5b41ea7cf7c28f47cd0f1829409ae39852bab4f 100644
--- a/src/mips/stub-cache-mips.cc
+++ b/src/mips/stub-cache-mips.cc
@@ -1705,8 +1705,12 @@ 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;
 
@@ -1960,8 +1964,12 @@ 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 = a1;