Index: src/wp-admin/css/customize-controls.css
===================================================================
--- src/wp-admin/css/customize-controls.css	(revision 42039)
+++ src/wp-admin/css/customize-controls.css	(working copy)
@@ -550,7 +550,7 @@
 }
 
 #customize-controls #customize-theme-controls .customize-themes-panel .accordion-section-title {
-	color: #555;
+	color: #555d66;
 	background-color: #fff;
 	border-left: 4px solid #fff;
 }
@@ -2147,31 +2147,6 @@
 	margin: 1px 0;
 }
 
-/* Unstick the filter bar on short windows/screens. This breakpoint is based on the
-   current length of .org feature filters assuming translations do not wrap lines. */
-@media screen and (max-height:540px), screen and (max-width:1018px) {
-	.customize-preview-header.themes-filter-bar {
-		position: relative;
-		left: 0;
-		width: 100%;
-		margin: 0 0 25px 0;
-	}
-	.filter-drawer {
-		top: 46px;
-	}
-	.wp-customizer .theme-browser .themes {
-		padding: 0 0 25px 25px;
-		overflow: hidden;
-	}
-
-	.control-panel-themes .customize-themes-full-container {
-		margin-top: 0;
-		padding: 0;
-		height: 100%;
-		width: calc(100% - 300px);
-	}
-}
-
 @media screen and (max-width:1018px) {
 	.filter-drawer .filter-group {
 		width: calc( (100% - 50px) / 2);
@@ -2197,6 +2172,10 @@
 	.control-panel-themes .filter-themes-count {
 		float: left;
 	}
+	
+	.wp-customizer .theme-browser .themes {
+		margin-top: 39px;
+	}
 }
 
 @media screen and (max-width:792px) {
@@ -2212,6 +2191,16 @@
 /* Mobile - toggle between themes and filters */
 @media screen and (max-width:600px) {
 
+	.customize-preview-header.themes-filter-bar {
+		width: 100%;
+		left: 0;
+		top: 46px;
+	}
+
+	.wp-customizer .theme-browser .themes {
+		margin-top: 111px;
+	}
+
 	.filter-drawer {
 		top: 132px;
 	}
Index: src/wp-admin/js/customize-controls.js
===================================================================
--- src/wp-admin/js/customize-controls.js	(revision 42039)
+++ src/wp-admin/js/customize-controls.js	(working copy)
@@ -1901,11 +1902,11 @@
 					.parent().next( '.filter-drawer' ).slideToggle( 180, 'linear' );
 
 				if ( $filterToggle.hasClass( 'open' ) ) {
-					var marginOffset = 1018 < window.innerWidth ? 50 : 76;
+					var marginOffset = 1018 < window.innerWidth ? 50 : 111;
 
 					section.contentContainer.find( '.themes' ).css( 'margin-top', section.filtersHeight + marginOffset );
 				} else {
-					section.contentContainer.find( '.themes' ).css( 'margin-top', 0 );
+					section.contentContainer.find( '.themes' ).css( 'margin-top', ( 600 < window.innerWidth ? 0 : 111 ) );
 				}
 			});