diff -u b/core/includes/form.inc b/core/includes/form.inc
--- b/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -1169,7 +1169,7 @@
     // allow the value of the clicked button to be retained in its normal
     // $form_state['values'] locations, even if these locations are not included
     // in #limit_validation_errors.
-    if (isset($form_state['triggering_element']['#button_type'])) {
+    if (!empty($form_state['triggering_element']['#is_button'])) {
       $button_value = $form_state['triggering_element']['#value'];
 
       // Like all input controls, the button value may be in the location
@@ -1947,7 +1947,7 @@
     }
 
     // Special processing if the triggering element is a button.
-    if (isset($form_state['triggering_element']['#button_type'])) {
+    if (!empty($form_state['triggering_element']['#is_button'])) {
       // Because there are several ways in which the triggering element could
       // have been determined (including from input variables set by JavaScript
       // or fallback behavior implemented for IE), and because buttons often
@@ -2083,7 +2083,7 @@
     // If the form was submitted by the browser rather than via Ajax, then it
     // can only have been triggered by a button, and we need to determine which
     // button within the constraints of how browsers provide this information.
-    if (isset($element['#button_type'])) {
+    if (!empty($element['#is_button'])) {
       // All buttons in the form need to be tracked for
       // form_state_values_clean() and for the form_builder() code that handles
       // a form submission containing no button information in $_POST.
@@ -3925,7 +3925,7 @@
  * @param $variables
  *   An associative array containing:
  *   - element: An associative array containing the properties of the element.
- *     Properties used: #attributes, #button_type, #button_class, #name, #value.
+ *     Properties used: #attributes, #button_type, #name, #value.
  *
  * @ingroup themeable
  */
@@ -3935,8 +3935,8 @@
   element_set_attributes($element, array('id', 'name', 'value'));
 
   $element['#attributes']['class'][] = 'form-button';
-  if (!empty($element['#button_class'])) {
-    $element['#attributes']['class'][] = 'form-button-' . $element['#button_class'];
+  if (!empty($element['#button_type'])) {
+    $element['#attributes']['class'][] = 'form-button-' . $element['#button_type'];
   }
   else {
     $element['#attributes']['class'][] = 'form-submit';
@@ -3954,8 +3954,7 @@
  * @param $variables
  *   An associative array containing:
  *   - element: An associative array containing the properties of the element.
- *     Properties used: #attributes, #button_type, #button_class, #name,
- *     #value, #title, #src.
+ *     Properties used: #attributes, #button_type, #name, #value, #title, #src.
  *
  * @ingroup themeable
  */
@@ -3971,8 +3970,8 @@
   }
 
   $element['#attributes']['class'][] = 'form-button';
-  if (!empty($element['#button_class'])) {
-    $element['#attributes']['class'][] = 'form-button-' . $element['#button_class'];
+  if (!empty($element['#button_type'])) {
+    $element['#attributes']['class'][] = 'form-button-' . $element['#button_type'];
   }
   else {
     $element['#attributes']['class'][] = 'form-submit';
diff -u b/core/lib/Drupal/Core/Entity/EntityFormController.php b/core/lib/Drupal/Core/Entity/EntityFormController.php
--- b/core/lib/Drupal/Core/Entity/EntityFormController.php
+++ b/core/lib/Drupal/Core/Entity/EntityFormController.php
@@ -99,12 +99,12 @@
       $delete = $element['delete'];
       unset($element['delete']);
       $element['delete'] = $delete;
-      $element['delete']['#button_class'] = 'delete';
+      $element['delete']['#button_type'] = 'delete';
     }
 
     if (isset($element['submit'])) {
-      // Give the primary submit button a #button_class of primary.
-      $element['submit']['#button_class'] = 'primary';
+      // Give the primary submit button a #button_type of primary.
+      $element['submit']['#button_type'] = 'primary';
     }
 
     $count = 0;
only in patch2:
unchanged:
--- a/core/includes/ajax.inc
+++ b/core/includes/ajax.inc
@@ -631,7 +631,7 @@ function ajax_pre_render_element($element) {
       // If the element is a (non-image) button, its name may not identify it
       // uniquely, in which case a match on value is also needed.
       // @see _form_button_was_clicked()
-      if (isset($element['#button_type']) && empty($element['#has_garbage_value'])) {
+      if (!empty($element['#is_button']) && empty($element['#has_garbage_value'])) {
         $settings['submit']['_triggering_element_value'] = $element['#value'];
       }
     }
only in patch2:
unchanged:
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -300,7 +300,7 @@ function system_element_info() {
   $types['submit'] = array(
     '#input' => TRUE,
     '#name' => 'op',
-    '#button_type' => 'submit',
+    '#is_button' => TRUE,
     '#executes_submit_callback' => TRUE,
     '#limit_validation_errors' => FALSE,
     '#process' => array('form_process_button', 'ajax_process_form'),
@@ -309,7 +309,7 @@ function system_element_info() {
   $types['button'] = array(
     '#input' => TRUE,
     '#name' => 'op',
-    '#button_type' => 'submit',
+    '#is_button' => TRUE,
     '#executes_submit_callback' => FALSE,
     '#limit_validation_errors' => FALSE,
     '#process' => array('form_process_button', 'ajax_process_form'),
@@ -317,7 +317,7 @@ function system_element_info() {
   );
   $types['image_button'] = array(
     '#input' => TRUE,
-    '#button_type' => 'submit',
+    '#is_button' => TRUE,
     '#executes_submit_callback' => TRUE,
     '#limit_validation_errors' => FALSE,
     '#process' => array('form_process_button', 'ajax_process_form'),
only in patch2:
unchanged:
--- a/core/modules/views/views_ui/admin.inc
+++ b/core/modules/views/views_ui/admin.inc
@@ -2303,7 +2303,7 @@ function views_fetch_fields($base, $type, $grouping = FALSE, $sub_type = NULL) {
  */
 function views_ui_form_button_was_clicked($element, &$form_state) {
   $process_input = empty($element['#disabled']) && ($form_state['programmed'] || ($form_state['process_input'] && (!isset($element['#access']) || $element['#access'])));
-  if ($process_input && !isset($form_state['triggering_element']) && isset($element['#button_type']) && isset($form_state['input'][$element['#name']]) && isset($element['#values']) && in_array($form_state['input'][$element['#name']], $element['#values'], TRUE)) {
+  if ($process_input && !isset($form_state['triggering_element']) && !empty($element['#is_button']) && isset($form_state['input'][$element['#name']]) && isset($element['#values']) && in_array($form_state['input'][$element['#name']], $element['#values'], TRUE)) {
     $form_state['triggering_element'] = $element;
   }
   return $element;