Index: src/wp-admin/css/customize-controls.css
===================================================================
--- src/wp-admin/css/customize-controls.css	(revision 33526)
+++ src/wp-admin/css/customize-controls.css	(working copy)
@@ -273,10 +273,6 @@
 	left: -100%;
 }
 
-.section-open .control-panel-back {
-	display: none;
-}
-
 .accordion-sub-container.control-panel-content {
 	display: none;
 	position: absolute;
@@ -329,22 +325,6 @@
 	border-left: 1px solid #ddd;
 }
 
-.control-panel-back {
-	display: block;
-	position: fixed;
-	top: 0;
-	z-index: 99;
-	left: -48px;
-	width: 45px;
-	height: 45px;
-	padding-right: 2px;
-	background: #eee;
-	border-right: 1px solid #ddd;
-	cursor: pointer;
-	-webkit-transition: left .18s ease-in-out, color .1s ease-in-out, background .1s ease-in-out;
-	transition: left .18s ease-in-out, color .1s ease-in-out, background .1s ease-in-out;
-}
-
 .customize-panel-back,
 .customize-section-back {
 	display: block;
@@ -367,7 +347,6 @@
 	height: 70px;
 }
 
-.ios .control-panel-back,
 .ios .customize-panel-back,
 .ios .customize-section-back {
 	-webkit-transition: left 0s;
@@ -374,7 +353,6 @@
 	transition: left 0s;
 }
 
-.collapsed .control-panel-back,
 .ios .customize-panel-back {
 	display: none;
 }
@@ -396,8 +374,6 @@
 .customize-overlay-close:hover,
 .customize-controls-close:focus,
 .customize-controls-close:hover,
-.control-panel-back:focus,
-.control-panel-back:hover,
 .customize-controls-preview-toggle:focus,
 .customize-controls-preview-toggle:hover {
 	background: #ddd;
@@ -436,14 +412,6 @@
 	left: 13px;
 }
 
-.control-panel-back:before {
-	font: normal 20px/45px dashicons;
-	content: "\f341";
-	position: relative;
-	top: 1px;
-	left: 13px;
-}
-
 .wp-full-overlay-sidebar .wp-full-overlay-header {
 	-webkit-transition: padding ease-in-out .18s;
 	transition: padding ease-in-out .18s;
Index: src/wp-admin/customize.php
===================================================================
--- src/wp-admin/customize.php	(revision 33526)
+++ src/wp-admin/customize.php	(working copy)
@@ -136,7 +136,6 @@
 				<a class="customize-controls-close" href="<?php echo esc_url( $return ); ?>">
 					<span class="screen-reader-text"><?php _e( 'Cancel' ); ?></span>
 				</a>
-				<span class="control-panel-back" tabindex="-1"><span class="screen-reader-text"><?php _e( 'Back' ); ?></span></span>
 			</div>
 			<div class="secondary-actions">
 				<button type="button" class="customize-overlay-close">
Index: src/wp-admin/js/customize-controls.js
===================================================================
--- src/wp-admin/js/customize-controls.js	(revision 33526)
+++ src/wp-admin/js/customize-controls.js	(working copy)
@@ -3387,18 +3387,6 @@
 			event.preventDefault();
 		});
 
-		// Go back to the top-level Customizer accordion.
-		$( '#customize-header-actions' ).on( 'click keydown', '.control-panel-back', function( event ) {
-			if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
-				return;
-			}
-
-			event.preventDefault(); // Keep this AFTER the key filter above
-			api.panel.each( function ( panel ) {
-				panel.collapse();
-			});
-		});
-
 		closeBtn.keydown( function( event ) {
 			if ( 9 === event.which ) // tab
 				return;