[serializer/debugger] hide scripts in the snapshot from the debugger.

test/cctest/test-serialize.cc

Index: test/cctest/test-serialize.cc
diff --git a/test/cctest/test-serialize.cc b/test/cctest/test-serialize.cc
index e8be36a32da43318448ba0e83d6a02bc96d8b3c4..153e3ff85d66bdbb4fb90df374f22d4b1ab45826 100644
--- a/test/cctest/test-serialize.cc
+++ b/test/cctest/test-serialize.cc
@@ -638,6 +638,11 @@ TEST(CustomSnapshotDataBlob1) {
         CompileRun("f()")->Int32Value(isolate1->GetCurrentContext());
     CHECK_EQ(42, result.FromJust());
     CHECK(CompileRun("this.g")->IsUndefined());
+    v8::Local<v8::Value> f = CompileRun("f");
+    i::Handle<i::JSFunction> function =
+        i::Handle<i::JSFunction>::cast(v8::Utils::OpenHandle(*f));
+    // Being part of the snapshot hides a script from the debugger.
+    CHECK(!function->shared()->IsSubjectToDebugging());
   }
   isolate1->Dispose();
 }