[debugger] fix break locations for assignments and return.

test/mjsunit/debug-step-end-of-script.js

Index: test/mjsunit/debug-step-end-of-script.js
diff --git a/test/mjsunit/debug-step-end-of-script.js b/test/mjsunit/debug-step-end-of-script.js
index ded58d1dad9fb201f4194910ba26e7c04de56f9b..e8ffcc8bc1c1d18fbf804257128a575929b6f1ed 100644
--- a/test/mjsunit/debug-step-end-of-script.js
+++ b/test/mjsunit/debug-step-end-of-script.js
@@ -5,7 +5,7 @@
 // Flags: --expose-debug-as debug --allow-natives-syntax
 
 var Debug = debug.Debug;
-var expected = ["debugger;", "", "debugger;"];
+var expected = ["debugger;", "debugger;"];
 
 function listener(event, exec_state, event_data, data) {
   if (event != Debug.DebugEvent.Break) return;