[generators] Perform state dispatch in loop header.

test/mjsunit/harmony/generators.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: --ignition-generators --harmony-do-expressions
 
 
 { // yield in try-catch
 
   let g = function*() {
@@ skipping 557 matching lines @@
     yield 42;
     yield 42;
     yield 42;
   }
   g = foo();
   for (let i = 0; i < 100; ++i) {
     assertEquals({value: 42, done: false}, g.next());
   }
   assertEquals({value: undefined, done: true}, g.next());
 }
+
+{
+  function* foo() {
+    for (let i = 0; i < 3; ++i) {
+      let j = 0
+      yield i;
+      do {
+        yield (i + 10);
+      } while (++j < 2);
+    }
+  }
+  g = foo();
+  assertEquals({value: 0, done: false}, g.next());
+  assertEquals({value: 10, done: false}, g.next());
+  assertEquals({value: 10, done: false}, g.next());
+  assertEquals({value: 1, done: false}, g.next());
+  assertEquals({value: 11, done: false}, g.next());
+  assertEquals({value: 11, done: false}, g.next());
+  assertEquals({value: 2, done: false}, g.next());
+  assertEquals({value: 12, done: false}, g.next());
+  assertEquals({value: 12, done: false}, g.next());
+  assertEquals({value: undefined, done: true}, g.next());
+}