[strong] Remove all remainders of strong mode

src/d8.cc

Index: src/d8.cc
diff --git a/src/d8.cc b/src/d8.cc
index 7947c3f96957ba53565eb54ce1751da165b7cf0d..e306f728aa62464cd70fc3af26be07f25625c3c7 100644
--- a/src/d8.cc
+++ b/src/d8.cc
@@ -1058,20 +1058,7 @@ void Shell::AddHistogramSample(void* histogram, int sample) {
 }
 
 
-class NoUseStrongForUtilityScriptScope {
- public:
-  NoUseStrongForUtilityScriptScope() : flag_(i::FLAG_use_strong) {
-    i::FLAG_use_strong = false;
-  }
-  ~NoUseStrongForUtilityScriptScope() { i::FLAG_use_strong = flag_; }
-
- private:
-  bool flag_;
-};
-
-
 void Shell::InstallUtilityScript(Isolate* isolate) {
-  NoUseStrongForUtilityScriptScope no_use_strong;
   HandleScope scope(isolate);
   // If we use the utility context, we have to set the security tokens so that
   // utility, evaluation and debug context can all access each other.