views::Textfield: Implement yank editing command.

ui/views/controls/textfield/textfield_model_unittest.cc

Index: ui/views/controls/textfield/textfield_model_unittest.cc
diff --git a/ui/views/controls/textfield/textfield_model_unittest.cc b/ui/views/controls/textfield/textfield_model_unittest.cc
index 3663816813076c8039b37d1455dad763eb97b0c6..0f67020590b7b0eeca703d94c78d226f4acc2407 100644
--- a/ui/views/controls/textfield/textfield_model_unittest.cc
+++ b/ui/views/controls/textfield/textfield_model_unittest.cc
@@ -1653,4 +1653,52 @@ TEST_F(TextfieldModelTest, Transpose) {
   }
 }
 
+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