only in patch2:
unchanged:
--- /dev/null
+++ b/core/themes/stable/css/core/splitbutton/splitbutton.css
@@ -0,0 +1,111 @@
+.splitbutton * {
+  box-sizing: border-box;
+}
+
+.splitbutton *:focus {
+  outline: none;
+  box-shadow: 0 0 0 2px #0071b3;
+}
+
+.js .splitbutton__toggle {
+  position: relative;
+  border-radius: 0 20em 20em 0;
+  background-color: #e8e8e8;
+  background-image: -webkit-linear-gradient(top, #e8e8e8, #d2d2d2);
+  background-image: linear-gradient(to bottom, #e8e8e8, #d2d2d2);
+}
+
+.splitbutton__toggle:focus {
+  z-index: 5;
+}
+
+.js .splitbutton__main-button {
+  border-radius: 20em 0 0 20em;
+}
+
+.splitbutton__toggle-arrow {
+  position: absolute;
+  top: 50%;
+  right: 38%;
+  display: block;
+  overflow: hidden;
+  width: 0;
+  height: 0;
+  margin-top: -0.1666em;
+  border-width: 0.3333em 0.3333em 0;
+  border-style: solid;
+  border-right-color: transparent;
+  border-bottom-color: transparent;
+  border-left-color: transparent;
+  line-height: 0;
+}
+.splitbutton.open .splitbutton__toggle-arrow {
+  top: 58%;
+  right: 53%;
+  transform: translate(50%, -50%) rotate(180deg);
+}
+
+.splitbutton__title--toggle {
+  position: relative;
+  padding-right: 2.5em; /* LTR */
+}
+
+.splitbutton__title--toggle::after {
+  position: absolute;
+  top: 52%;
+  right: 14px;
+  width: 0;
+  height: 0;
+  content: "";
+  transform: translate(50%, -50%) rotate(0);
+  border-width: 0.3333em 0.3333em 0;
+  border-style: solid;
+  border-right-color: transparent;
+  border-bottom-color: transparent;
+  border-left-color: transparent;
+}
+.splitbutton.open .splitbutton__title--toggle::after {
+  top: 48%;
+  transform: translate(50%, -50%) rotate(180deg);
+}
+
+.js .splitbutton__operation-list {
+  padding-top: 2px;
+}
+
+.js .splitbutton__operation-list li:first-child {
+  border-radius: 0.5em 0.5em 0 0;
+}
+.js .splitbutton__operation-list li:last-child {
+  border-radius: 0 0 0.5em 0.5em;
+}
+
+.js .splitbutton__operation-list-item {
+  width: 100%;
+  margin: 0;
+  padding: 0.25em 1.063em;
+  text-align: left;
+  color: #3a3a3a;
+  border: 1px solid #a6a6a6;
+  border-top-width: 0;
+  border-bottom-width: 0;
+  border-radius: 0;
+  background-color: #fff;
+  background-image: -webkit-linear-gradient(top, #f3f3f3, #e8e8e8);
+  background-image: linear-gradient(to bottom, #f3f3f3, #e8e8e8);
+  font-family: "Lucida Grande", "Lucida Sans Unicode", Verdana, sans-serif;
+  font-size: 0.875rem;
+  font-weight: normal;
+}
+.js .splitbutton__operation-list-item:hover {
+  background: #dedede;
+}
+
+.js .splitbutton__operation-list li:first-child .splitbutton__operation-list-item {
+  border-top-width: 1px;
+  border-radius: 0.5em 0.5em 0 0;
+}
+.js .splitbutton__operation-list li:last-child .splitbutton__operation-list-item {
+  border-bottom-width: 1px;
+  border-radius: 0 0 0.5em 0.5em;
+}
only in patch2:
unchanged:
--- a/core/themes/stable/stable.info.yml
+++ b/core/themes/stable/stable.info.yml
@@ -92,6 +92,11 @@ libraries-override:
   # Load version 3.0.3 of normalize.css for backwards compatibility.
   core/normalize: stable/normalize
 
+  core/drupal.splitbutton:
+    css:
+      component:
+        misc/splitbutton/splitbutton.css: css/core/splitbutton/splitbutton.css
+
   dblog/drupal.dblog:
     css:
       component:
only in patch2:
unchanged:
--- /dev/null
+++ b/core/themes/stable9/css/core/splitbutton/splitbutton.css
@@ -0,0 +1,111 @@
+.splitbutton * {
+  box-sizing: border-box;
+}
+
+.splitbutton *:focus {
+  outline: none;
+  box-shadow: 0 0 0 2px #0071b3;
+}
+
+.js .splitbutton__toggle {
+  position: relative;
+  border-radius: 0 20em 20em 0;
+  background-color: #e8e8e8;
+  background-image: -webkit-linear-gradient(top, #e8e8e8, #d2d2d2);
+  background-image: linear-gradient(to bottom, #e8e8e8, #d2d2d2);
+}
+
+.splitbutton__toggle:focus {
+  z-index: 5;
+}
+
+.js .splitbutton__main-button {
+  border-radius: 20em 0 0 20em;
+}
+
+.splitbutton__toggle-arrow {
+  position: absolute;
+  top: 50%;
+  right: 38%;
+  display: block;
+  overflow: hidden;
+  width: 0;
+  height: 0;
+  margin-top: -0.1666em;
+  border-width: 0.3333em 0.3333em 0;
+  border-style: solid;
+  border-right-color: transparent;
+  border-bottom-color: transparent;
+  border-left-color: transparent;
+  line-height: 0;
+}
+.splitbutton.open .splitbutton__toggle-arrow {
+  top: 58%;
+  right: 53%;
+  transform: translate(50%, -50%) rotate(180deg);
+}
+
+.splitbutton__title--toggle {
+  position: relative;
+  padding-right: 2.5em; /* LTR */
+}
+
+.splitbutton__title--toggle::after {
+  position: absolute;
+  top: 52%;
+  right: 14px;
+  width: 0;
+  height: 0;
+  content: "";
+  transform: translate(50%, -50%) rotate(0);
+  border-width: 0.3333em 0.3333em 0;
+  border-style: solid;
+  border-right-color: transparent;
+  border-bottom-color: transparent;
+  border-left-color: transparent;
+}
+.splitbutton.open .splitbutton__title--toggle::after {
+  top: 48%;
+  transform: translate(50%, -50%) rotate(180deg);
+}
+
+.js .splitbutton__operation-list {
+  padding-top: 2px;
+}
+
+.js .splitbutton__operation-list li:first-child {
+  border-radius: 0.5em 0.5em 0 0;
+}
+.js .splitbutton__operation-list li:last-child {
+  border-radius: 0 0 0.5em 0.5em;
+}
+
+.js .splitbutton__operation-list-item {
+  width: 100%;
+  margin: 0;
+  padding: 0.25em 1.063em;
+  text-align: left;
+  color: #3a3a3a;
+  border: 1px solid #a6a6a6;
+  border-top-width: 0;
+  border-bottom-width: 0;
+  border-radius: 0;
+  background-color: #fff;
+  background-image: -webkit-linear-gradient(top, #f3f3f3, #e8e8e8);
+  background-image: linear-gradient(to bottom, #f3f3f3, #e8e8e8);
+  font-family: "Lucida Grande", "Lucida Sans Unicode", Verdana, sans-serif;
+  font-size: 0.875rem;
+  font-weight: normal;
+}
+.js .splitbutton__operation-list-item:hover {
+  background: #dedede;
+}
+
+.js .splitbutton__operation-list li:first-child .splitbutton__operation-list-item {
+  border-top-width: 1px;
+  border-radius: 0.5em 0.5em 0 0;
+}
+.js .splitbutton__operation-list li:last-child .splitbutton__operation-list-item {
+  border-bottom-width: 1px;
+  border-radius: 0 0 0.5em 0.5em;
+}
only in patch2:
unchanged:
--- a/core/themes/stable9/stable9.info.yml
+++ b/core/themes/stable9/stable9.info.yml
@@ -92,6 +92,11 @@ libraries-override:
   # Load version 3.0.3 of normalize.css for backwards compatibility.
   core/normalize: stable/normalize
 
+  core/drupal.splitbutton:
+    css:
+      component:
+        misc/splitbutton/splitbutton.css: css/core/splitbutton/splitbutton.css
+
   dblog/drupal.dblog:
     css:
       component: