views::Textfield: Implement yank editing command.

ui/views/test/views_test_helper.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "ui/views/controls/textfield/textfield_model.h"
 #include "ui/views/test/views_test_helper.h"
 
 namespace views {
 
 ViewsTestHelper::ViewsTestHelper() {
 }
 
 ViewsTestHelper::~ViewsTestHelper() {
+  // Clear kill buffer used for "Yank" text editing command so that no state
+  // persists between tests.
+  TextfieldModel::ClearKillBufferForTesting();

[msw, 2016/07/22 17:44:03]

Would it be sufficient to clear this in Textfield[Model]Test::TearDown, or at
the start/end of the yank text fixtures? Other unit test fixtures that actually
use yank could do the same, and any other unit test fixtures that don't actually
use yank shouldn't be affected, right?

[karandeepb, 2016/07/25 06:38:11]

Done. 

 }
 
 void ViewsTestHelper::SetUp() {
 }
 
 void ViewsTestHelper::TearDown() {
 }
 
 gfx::NativeWindow ViewsTestHelper::GetContext() {
   return NULL;
 }
 
 }  // namespace views