Revert "Fix fromEnvironment when called from isolates."

runtime/lib/bool.cc

Index: runtime/lib/bool.cc
diff --git a/runtime/lib/bool.cc b/runtime/lib/bool.cc
index b4d69f536eebc34eff7a7fea9136f03c385402b6..d57574568dd127bfdfcd15ee92b40bbc6cd3f9ad 100644
--- a/runtime/lib/bool.cc
+++ b/runtime/lib/bool.cc
@@ -21,7 +21,6 @@ DEFINE_NATIVE_ENTRY(Bool_fromEnvironment, 3) {
   GET_NON_NULL_NATIVE_ARGUMENT(String, name, arguments->NativeArgAt(1));
   GET_NATIVE_ARGUMENT(Bool, default_value, arguments->NativeArgAt(2));
   // Call the embedder to supply us with the environment.
-  Dart_EnterScope();
   Dart_EnvironmentCallback callback = isolate->environment_callback();
   if (callback != NULL) {
     Dart_Handle result = callback(Api::NewHandle(isolate, name.raw()));
@@ -41,7 +40,6 @@ DEFINE_NATIVE_ENTRY(Bool_fromEnvironment, 3) {
           String::Handle(String::New("Illegal environment value")));
     }
   }
-  Dart_ExitScope();
   return default_value.raw();
 }