views::Textfield: Implement yank editing command.

ui/views/controls/textfield/textfield_model_unittest.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 <stddef.h>
 
 #include <memory>
 #include <vector>
@@ skipping 1635 matching lines @@
       model.SelectRange(test_case.range);
       EXPECT_EQ(test_case.range, model.render_text()->selection());
       model.Transpose();
 
       EXPECT_EQ(test_case.expected_text, model.text());
       EXPECT_EQ(test_case.expected_selection, model.render_text()->selection());
     }
   }
 }
 
+TEST_F(TextfieldModelTest, Yank) {
+  TextfieldModel model(nullptr);
+  model.SetText(base::ASCIIToUTF16("abcde"));
+  model.SelectRange(gfx::Range(1,3));
+
+  // Delete selection but don't add to kill buffer.
+  model.Delete(false);
+  EXPECT_STR_EQ("ade", model.text());
+
+  // Since the kill buffer is empty, yank should cause no change.
+  model.Yank();
+  EXPECT_STR_EQ("ade", model.text());
+
+  // Delete selection and add to kill buffer.
+  model.SelectRange(gfx::Range(0,1));
+  model.Delete(true);
+  EXPECT_STR_EQ("de", model.text());
+
+  // Yank twice.
+  model.Yank();
+  model.Yank();
+  EXPECT_STR_EQ("aade", model.text());
+
+  // Ensure an empty deletion does not modify the kill buffer.
+  model.SelectRange(gfx::Range(4));
+  model.Delete(true);
+  model.Yank();
+  EXPECT_STR_EQ("aadea", model.text());
+
+  // Backspace twice but don't add to kill buffer.
+  model.Backspace(false);
+  model.Backspace(false);
+  EXPECT_STR_EQ("aad", model.text());
+
+  // Ensure kill buffer is not modified.
+  model.Yank();
+  EXPECT_STR_EQ("aada", model.text());
+
+  // Backspace twice, each time modifying the kill buffer.
+  model.Backspace(true);
+  model.Backspace(true);
+  EXPECT_STR_EQ("aa", model.text());
+
+  // Ensure yanking inserts the modified kill buffer text.
+  model.Yank();
+  EXPECT_STR_EQ("aad", model.text());
+}
+
 }  // namespace views