Fix Debug::Break crash.

src/execution.cc

 // Copyright 2012 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 114 matching lines @@
   // Update the pending exception flag and return the value.
   *has_pending_exception = value->IsException();
   ASSERT(*has_pending_exception == Isolate::Current()->has_pending_exception());
   if (*has_pending_exception) {
     isolate->ReportPendingMessages();
     if (isolate->pending_exception() == Failure::OutOfMemoryException()) {
       if (!isolate->ignore_out_of_memory()) {
         V8::FatalProcessOutOfMemory("JS", true);
       }
     }
+#ifdef ENABLE_DEBUGGER_SUPPORT
+    // Reset stepping state when script exits with uncaught exception.
+    if (isolate->debugger()->IsDebuggerActive()) {
+      isolate->debug()->ClearStepping();
+    }
+#endif  // ENABLE_DEBUGGER_SUPPORT
     return Handle<Object>();
   } else {
     isolate->clear_pending_message();
   }
 
   return Handle<Object>(value->ToObjectUnchecked(), isolate);
 }
 
 
 Handle<Object> Execution::Call(Handle<Object> callable,
@@ skipping 775 matching lines @@
   }
   if (stack_guard->IsInterrupted()) {
     stack_guard->Continue(INTERRUPT);
     return isolate->StackOverflow();
   }
   return isolate->heap()->undefined_value();
 }
 
 
 } }  // namespace v8::internal