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

test/mjsunit/es6/debug-blockscopes.js

Index: test/mjsunit/es6/debug-blockscopes.js
diff --git a/test/mjsunit/es6/debug-blockscopes.js b/test/mjsunit/es6/debug-blockscopes.js
index 3f890ebd546d2edba74066f0fd5e5c031ce91ec6..d3c36207f1dc27bdef41e6ed963743448a63f641 100644
--- a/test/mjsunit/es6/debug-blockscopes.js
+++ b/test/mjsunit/es6/debug-blockscopes.js
@@ -26,6 +26,7 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Flags: --expose-debug-as debug --allow-natives-syntax
+// Flags: --debug-eval-readonly-locals
 // The functions used for testing backtraces. They are at the top to make the
 // testing of source line/column easier.
 
@@ -525,15 +526,12 @@ function shadowing_1() {
   {
     let i = 5;
     debugger;
-    assertEqualsUnlessOptimized(27, i, shadowing_1);
   }
   assertEquals(0, i);
-  debugger;
-  assertEqualsUnlessOptimized(27, i, shadowing_1);
 }
 
 listener_delegate = function (exec_state) {
-  exec_state.frame(0).evaluate("i = 27");
+  assertEqualsUnlessOptimized(5, exec_state.frame(0).evaluate("i").value());
 }
 shadowing_1();
 EndTest();
@@ -546,13 +544,12 @@ function shadowing_2() {
   {
     let j = 5;
     debugger;
-    assertEqualsUnlessOptimized(27, j, shadowing_2);
   }
-  assertEqualsUnlessOptimized(0, i, shadowing_2);
 }
 
 listener_delegate = function (exec_state) {
-  exec_state.frame(0).evaluate("j = 27");
+  assertEqualsUnlessOptimized(0, exec_state.frame(0).evaluate("i").value());
+  assertEqualsUnlessOptimized(5, exec_state.frame(0).evaluate("j").value());
 }
 shadowing_2();
 EndTest();