Enable preemption in d8.

src/runtime.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3754 matching lines @@
 static Object* Runtime_DebugBreak(Arguments args) {
   ASSERT(args.length() == 0);
   return Execution::DebugBreakHelper();
 }
 
 
 static Object* Runtime_StackGuard(Arguments args) {
   ASSERT(args.length() == 1);
 
   // First check if this is a real stack overflow.
-  if (StackGuard::IsStackOverflow()) return Runtime_StackOverflow(args);
+  if (StackGuard::IsStackOverflow()) {
+    return Runtime_StackOverflow(args);
+  }
 
   return Execution::HandleStackGuardInterrupt();
 }
 
 
 // NOTE: These PrintXXX functions are defined for all builds (not just
 // DEBUG builds) because we may want to be able to trace function
 // calls in all modes.
 static void PrintString(String* str) {
   // not uncommon to have empty strings
@@ skipping 2302 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage();
   }
 }
 
 
 } }  // namespace v8::internal