Revert "Enable Object.observe by default"

test/cctest/test-microtask-delivery.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 18 matching lines @@
 
 #include "cctest.h"
 
 using namespace v8;
 namespace i = v8::internal;
 
 namespace {
 class HarmonyIsolate {
  public:
   HarmonyIsolate() {
+    i::FLAG_harmony_observation = true;
     i::FLAG_harmony_promises = true;
     isolate_ = Isolate::New();
     isolate_->Enter();
   }
 
   ~HarmonyIsolate() {
     isolate_->Exit();
     isolate_->Dispose();
   }
 
@@ skipping 78 matching lines @@
         "foo.id++;");
   }
   {
     LocalContext context4(isolate.GetIsolate());
     context4->Global()->Set(String::NewFromUtf8(isolate.GetIsolate(), "obj"),
                             obj);
     V8::RunMicrotasks(isolate.GetIsolate());
     CHECK_EQ(2, CompileRun("obj.calls")->Int32Value());
   }
 }