Add an end to end test: virtual keyboard opens on click of text input

ui/keyboard/keyboard_test_util.h

+// Copyright 2017 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.
+
+#ifndef UI_KEYBOARD_KEYBOARD_TEST_UTIL_
+#define UI_KEYBOARD_KEYBOARD_TEST_UTIL_
+
+namespace keyboard {
+
+// Waits until the keyboard is shown. Return false if there is no keyboard
+// window created.
+bool WaitUntilShown();
+
+// Waits until the keyboard is hidden. Return false if there is no keyboard
+// window created.
+bool WaitUntilHidden();
+
+}  // namespace keyboard
+
+#endif  // UI_KEYBOARD_KEYBOARD_TEST_UTIL_