[debugger] Scope iterator should not visit inner function literals.

R=marja@chromium.org
BUG=chromium:621361

Review-Url: https://codereview.chromium.org/2185913003
Cr-Commit-Position: refs/heads/master@{#38087}

src/debug/debug-scopes.cc

@@ -792,6 +792,11 @@ void ScopeIterator::CopyContextExtensionToScopeObject(
 
 void ScopeIterator::GetNestedScopeChain(Isolate* isolate, Scope* scope,
                                         int position) {
+  if (scope->is_function_scope()) {
+    // Do not collect scopes of nested inner functions inside the current one.
+    Handle<JSFunction> function = frame_inspector_->GetFunction();
+    if (scope->end_position() < function->shared()->end_position()) return;
+  }
   if (scope->is_hidden()) {
     // We need to add this chain element in case the scope has a context
     // associated. We need to keep the scope chain and context chain in sync.

test/mjsunit/regress/regress-crbug-621361.js

+// 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
+
+var Debug = debug.Debug;
+var steps = 0;
+var exception = null;
+
+function listener(event, execState, eventData, data) {
+  if (event != Debug.DebugEvent.Break) return;
+  try {
+    assertEquals([ debug.ScopeType.Local,
+                   debug.ScopeType.Script,
+                   debug.ScopeType.Global],
+                 execState.frame().allScopes().map(s => s.scopeType()));
+    var x_value = execState.frame().evaluate("x").value();
+    if (steps < 2) {
+      assertEquals(undefined, x_value);
+      execState.prepareStep(Debug.StepAction.StepIn);
+    } else {
+      assertEquals("l => l", x_value.toString());
+    }
+    steps++;
+  } catch (e) {
+    exception = e;
+  }
+}
+
+Debug.setListener(listener);
+
+(function() {
+  debugger;
+  var x = l => l;
+})();
+
+Debug.setListener(null);
+assertNull(exception);
+assertEquals(3, steps);