Added a version of the v8::HandleScope constructor with an Isolate and use that consistently.

src/d8-posix.cc

Index: src/d8-posix.cc
diff --git a/src/d8-posix.cc b/src/d8-posix.cc
index 8a278e4e42edfc2d8443e170caa93b7bc3aaf515..1be782a241de2266283efc5f8eb61b3e686529db 100644
--- a/src/d8-posix.cc
+++ b/src/d8-posix.cc
@@ -449,7 +449,7 @@ static bool WaitForChild(int pid,
 
 // Implementation of the system() function (see d8.h for details).
 Handle<Value> Shell::System(const Arguments& args) {
-  HandleScope scope;
+  HandleScope scope(args.GetIsolate());
   int read_timeout = -1;
   int total_timeout = -1;
   if (!GetTimeouts(args, &read_timeout, &total_timeout)) return v8::Undefined();