[debugger] step-next across yield should not leave the generator.

test/debugger/debug/es6/debug-stepnext-generators.js

Index: test/debugger/debug/es6/debug-stepnext-generators.js
diff --git a/test/debugger/debug/es6/debug-stepnext-generators.js b/test/debugger/debug/es6/debug-stepnext-generators.js
new file mode 100644
index 0000000000000000000000000000000000000000..966030076e7f707a7b8c2189d4c86a10d7d2f6eb
--- /dev/null
+++ b/test/debugger/debug/es6/debug-stepnext-generators.js
@@ -0,0 +1,48 @@
+// 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.
+
+Debug = debug.Debug
+var exception = null;
+var breaks = 0;
+
+function listener(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.Break) return;
+  try {
+    var source = exec_state.frame(0).sourceLineText();
+    assertTrue(RegExp(`B${breaks++}`).test(source));
+    if (/stop/.test(source)) return;
+    if (/step out/.test(source)) {
+      exec_state.prepareStep(Debug.StepAction.StepOut);
+    } else if (/step in/.test(source)) {
+      exec_state.prepareStep(Debug.StepAction.StepIn);
+    } else {
+      exec_state.prepareStep(Debug.StepAction.StepNext);
+    }
+  } catch (e) {
+    print(e, e.stack);
+    exception = e;
+  }
+}
+
+Debug.setListener(listener);
+
+function * g() {
+  debugger;  // B0
+  yield 1;   // B1
+  yield 2;   // B2 step out
+  yield 3;   // B5
+  yield 4;   // B6 step out
+  return 2 * (yield 5);
+}
+
+var i = g();
+assertEquals(1, i.next().value);
+assertEquals(2, i.next().value);   // B3
+assertEquals(3, i.next().value);   // B4 step in
+assertEquals(4, i.next().value);   // B7
+assertEquals(5, i.next().value);   // B8
+assertEquals(6, i.next(3).value);  // B9 stop
+
+assertNull(exception);
+assertEquals(10, breaks);