Administration: Improve the usage of the button CSS classes.

Introduces some consistency in the usage of the button CSS classes, fixes the
focus style for accessibility and responsiveness of the buttons.

- Adds the `button` class to all primary buttons make them responsive
- Removes all `secondary-button` classes and replaces it with button when needed. `button-secondary` shouldn't be used and exists just for backward compatibility reasons
- Replaces classes inside `submit_button()` with a shorthand for some buttons, and use an empty string for the default `button` class. Passing `button` is unnecessary
- Adjusts `get_submit_button()` to remove empty items

Props iseulde, dimchik, chris_d2d, mhowell, afercia.
Fixes #27314, #37138, #37448.


git-svn-id: https://develop.svn.wordpress.org/trunk@38672 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-customize-nav-menus.php

@@ -914,7 +914,7 @@ final class WP_Customize_Nav_Menus {
 					</p>
 					<p class="button-controls">
 						<span class="add-to-menu">
-							<input type="submit" class="button-secondary submit-add-to-menu right" value="<?php esc_attr_e( 'Add to Menu' ); ?>" name="add-custom-menu-item" id="custom-menu-item-submit">
+							<input type="submit" class="button submit-add-to-menu right" value="<?php esc_attr_e( 'Add to Menu' ); ?>" name="add-custom-menu-item" id="custom-menu-item-submit">
 							<span class="spinner"></span>
 						</span>
 					</p>

src/wp-includes/class-wp-customize-widgets.php

@@ -712,7 +712,7 @@ final class WP_Customize_Widgets {
 					<% }); %>
 				</ul>
 				<div class="move-widget-actions">
-					<button class="move-widget-btn button-secondary" type="button">{btn}</button>
+					<button class="move-widget-btn button" type="button">{btn}</button>
 				</div>
 			</div>'
 		);

src/wp-includes/customize/class-wp-customize-nav-menu-control.php

@@ -48,7 +48,7 @@ class WP_Customize_Nav_Menu_Control extends WP_Customize_Control {
 	 */
 	public function content_template() {
 		?>
-		<button type="button" class="button-secondary add-new-menu-item" aria-label="<?php esc_attr_e( 'Add or remove menu items' ); ?>" aria-expanded="false" aria-controls="available-menu-items">
+		<button type="button" class="button add-new-menu-item" aria-label="<?php esc_attr_e( 'Add or remove menu items' ); ?>" aria-expanded="false" aria-controls="available-menu-items">
 			<?php _e( 'Add Items' ); ?>
 		</button>
 		<button type="button" class="button-link reorder-toggle" aria-label="<?php esc_attr_e( 'Reorder menu items' ); ?>" aria-describedby="reorder-items-desc-{{ data.menu_id }}">

src/wp-includes/customize/class-wp-customize-new-menu-section.php

@@ -36,7 +36,7 @@ class WP_Customize_New_Menu_Section extends WP_Customize_Section {
 	protected function render() {
 		?>
 		<li id="accordion-section-<?php echo esc_attr( $this->id ); ?>" class="accordion-section-new-menu">
-			<button type="button" class="button-secondary add-new-menu-item add-menu-toggle" aria-expanded="false">
+			<button type="button" class="button add-new-menu-item add-menu-toggle" aria-expanded="false">
 				<?php echo esc_html( $this->title ); ?>
 			</button>
 			<ul class="new-menu-section-content"></ul>

src/wp-includes/customize/class-wp-widget-area-customize-control.php

@@ -57,7 +57,7 @@ class WP_Widget_Area_Customize_Control extends WP_Customize_Control {
 	public function render_content() {
 		$id = 'reorder-widgets-desc-' . str_replace( array( '[', ']' ), array( '-', '' ), $this->id );
 		?>
-		<button type="button" class="button-secondary add-new-widget" aria-expanded="false" aria-controls="available-widgets">
+		<button type="button" class="button add-new-widget" aria-expanded="false" aria-controls="available-widgets">
 			<?php _e( 'Add a Widget' ); ?>
 		</button>
 		<button type="button" class="button-link reorder-toggle" aria-label="<?php esc_attr_e( 'Reorder widgets' ); ?>" aria-describedby="<?php echo esc_attr( $id ); ?>">

src/wp-includes/general-template.php

@@ -481,7 +481,7 @@ function wp_login_form( $args = array() ) {
 			' . $login_form_middle . '
 			' . ( $args['remember'] ? '<p class="login-remember"><label><input name="rememberme" type="checkbox" id="' . esc_attr( $args['id_remember'] ) . '" value="forever"' . ( $args['value_remember'] ? ' checked="checked"' : '' ) . ' /> ' . esc_html( $args['label_remember'] ) . '</label></p>' : '' ) . '
 			<p class="login-submit">
-				<input type="submit" name="wp-submit" id="' . esc_attr( $args['id_submit'] ) . '" class="button-primary" value="' . esc_attr( $args['label_log_in'] ) . '" />
+				<input type="submit" name="wp-submit" id="' . esc_attr( $args['id_submit'] ) . '" class="button button-primary" value="' . esc_attr( $args['label_log_in'] ) . '" />
 				<input type="hidden" name="redirect_to" value="' . esc_url( $args['redirect'] ) . '" />
 			</p>
 			' . $login_form_bottom . '