Ensure that the ThreadInterrupter is awake after debugging

runtime/vm/debugger.cc

Index: runtime/vm/debugger.cc
diff --git a/runtime/vm/debugger.cc b/runtime/vm/debugger.cc
index 954aa8215c35cb2a349707a17fba7fa320d113f1..30ba2d992153e33fbcb6f84bfa1c9c2eef257bca 100644
--- a/runtime/vm/debugger.cc
+++ b/runtime/vm/debugger.cc
@@ -25,6 +25,7 @@
 #include "vm/stack_frame.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
+#include "vm/thread_interrupter.h"
 #include "vm/visitor.h"
 
 
@@ -2148,6 +2149,11 @@ void Debugger::HandleSteppingRequest(DebuggerStackTrace* stack_trace) {
       }
     }
   }
+  if (!isolate_->single_step()) {
+    // We are no longer single stepping, make sure that the ThreadInterrupter
+    // is awake.
+    ThreadInterrupter::WakeUp();
+  }
 }