[debugger] Hide scopes that originate from desugaring.

test/mjsunit/es6/debug-scope-default-param-with-eval.js

Index: test/mjsunit/es6/debug-scope-default-param-with-eval.js
diff --git a/test/mjsunit/es6/debug-scope-default-param-with-eval.js b/test/mjsunit/es6/debug-scope-default-param-with-eval.js
new file mode 100644
index 0000000000000000000000000000000000000000..bcfc38ceb5f27d91494a30f567d9d246231f99f3
--- /dev/null
+++ b/test/mjsunit/es6/debug-scope-default-param-with-eval.js
@@ -0,0 +1,57 @@
+// Copyright 2016 the V8 project authors. All rights reserved.
+// 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
+
+// Test that the parameter initialization block scope set up for
+// sloppy eval is visible to the debugger.
+
+var Debug = debug.Debug;
+var exception = null;
+var break_count = 0;
+
+function call_for_break() {
+  return 5;
+}
+
+function test(x = eval("var y = 7; debugger; y") + call_for_break()) {
+  return x;
+}
+
+function listener(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.Break) return;
+  try {
+    var frame = exec_state.frame(0);
+    var top_scope = frame.scope(0);
+    assertTrue(top_scope.scopeObject().propertyNames().includes('y'));
+    assertEquals(7, top_scope.scopeObject().property('y').value().value());
+    if (break_count++ == 0) {
+      // Inside eval.
+      assertEquals([ debug.ScopeType.Block,
+                     debug.ScopeType.Closure,
+                     debug.ScopeType.Script,
+                     debug.ScopeType.Global ],
+                   frame.allScopes().map(s => s.scopeType()));
+      exec_state.prepareStep(Debug.StepAction.StepOut);
+    } else {
+      // Outside of eval.
+      assertEquals([ debug.ScopeType.Block,
+                     debug.ScopeType.Local,
+                     debug.ScopeType.Script,
+                     debug.ScopeType.Global ],
+                   frame.allScopes().map(s => s.scopeType()));
+    }
+  } catch (e) {
+    exception = e;
+  }
+}
+
+Debug.setListener(listener);
+
+assertEquals(12, test());
+
+Debug.setListener(null);
+
+assertNull(exception);
+assertEquals(2, break_count);