Allow d8 to run a script multiple times, each time with a new context.

src/d8.cc

Index: src/d8.cc
diff --git a/src/d8.cc b/src/d8.cc
index e555c154847c81ef8ec62aa8717d81ac89759a7e..31beaf91fe03c9390978f1693ab20fb60e8059c7 100644
--- a/src/d8.cc
+++ b/src/d8.cc
@@ -1485,6 +1485,12 @@ int Shell::Main(int argc, char* argv[]) {
     }
     printf("======== Full Deoptimization =======\n");
     Testing::DeoptimizeAll();
+  } else if (i::FLAG_stress_runs > 0) {
+    int stress_runs = i::FLAG_stress_runs;
+    for (int i = 0; i < stress_runs && result == 0; i++) {
+      printf("============ Run %d/%d ============\n", i + 1, stress_runs);
+      result = RunMain(argc, argv);
+    }
   } else {
     result = RunMain(argc, argv);
   }