Do not reflect uninitialized 'let' and 'const' in scope mirrors.

test/mjsunit/harmony/debug-blockscopes.js

Index: test/mjsunit/harmony/debug-blockscopes.js
diff --git a/test/mjsunit/harmony/debug-blockscopes.js b/test/mjsunit/harmony/debug-blockscopes.js
index f3a0ab9cf093d8418a3677e28efbf9c71dd14ff9..8180377e6d399a8d48d9fc2ecdf10b9ab69028eb 100644
--- a/test/mjsunit/harmony/debug-blockscopes.js
+++ b/test/mjsunit/harmony/debug-blockscopes.js
@@ -481,3 +481,24 @@ listener_delegate = function(exec_state) {
 };
 for_loop_5();
 EndTest();
+
+
+// Uninitialized variables
+BeginTest("Uninitialized 1");
+
+function uninitialized_1() {
+  {
+    debugger;
+    let x = 1;
+  }
+}
+
+listener_delegate = function(exec_state) {
+  CheckScopeChain([debug.ScopeType.Block,
+                   debug.ScopeType.Local,
+                   debug.ScopeType.Script,
+                   debug.ScopeType.Global], exec_state);
+  CheckScopeContent({}, 0, exec_state);

[aandrey, 2014/12/08 13:12:22]

DevTools will not show empty Block scopes. Should I change this on our side?

[Dmitry Lomov (no reviews), 2014/12/08 14:34:09]

I do not know what is best here. This change makes variables invisible if you
break before the declaration. I think it is fine if we just not show empty block
scopes.

Another option would be to add not-yet-defined variables to block scopes with
'undefined' value. 

+};
+uninitialized_1();
+EndTest();