[debugger] debug-evaluate should not not modify local values.

test/mjsunit/debug-evaluate-modify-catch-block-scope.js

Index: test/mjsunit/debug-evaluate-modify-catch-block-scope.js
diff --git a/test/mjsunit/debug-evaluate-modify-catch-block-scope.js b/test/mjsunit/debug-evaluate-modify-catch-block-scope.js
index 63e30b7cf0e5e23d3f9047c68dcc32e361ccf2f9..07d6ccbe6f6c1ba31759445c39a92f7904482e9d 100644
--- a/test/mjsunit/debug-evaluate-modify-catch-block-scope.js
+++ b/test/mjsunit/debug-evaluate-modify-catch-block-scope.js
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --expose-debug-as debug
+// Flags: --expose-debug-as debug --debug-eval-readonly-locals
 
 Debug = debug.Debug
 
@@ -26,12 +26,12 @@ Debug.setListener(listener);
   } catch (e) {
     let a = 1;
     function bar() {
-      a = 2;  // this has no effect, when called from debug-eval
-      e = 2;  // this has no effect, when called from debug-eval.
+      a = 2;
+      e = 2;
     }
     debugger;
-    assertEquals(1, a);
-    assertEquals(1, e);
+    assertEquals(2, a);
+    assertEquals(2, e);
   }
 })();