Index: src/wp-admin/custom-background.php
===================================================================
--- src/wp-admin/custom-background.php	(revision 30687)
+++ src/wp-admin/custom-background.php	(working copy)
@@ -484,8 +484,15 @@
 	public function wp_set_background_image() {
 		if ( ! current_user_can('edit_theme_options') || ! isset( $_POST['attachment_id'] ) ) exit;
 		$attachment_id = absint($_POST['attachment_id']);
+
 		/** This filter is documented in wp-admin/includes/media.php */
-		$sizes = array_keys(apply_filters( 'image_size_names_choose', array('thumbnail' => __('Thumbnail'), 'medium' => __('Medium'), 'large' => __('Large'), 'full' => __('Full Size')) ));
+		$sizes = array_keys( apply_filters( 'image_size_names_choose', array(
+			'thumbnail' => __( 'Thumbnail' ),
+			'medium'    => __( 'Medium' ),
+			'large'     => __( 'Large' ),
+			'full'      => __( 'Full Size' )
+		), __FUNCTION__ ) );
+
 		$size = 'thumbnail';
 		if ( in_array( $_POST['size'], $sizes ) )
 			$size = esc_attr( $_POST['size'] );
Index: src/wp-admin/includes/media.php
===================================================================
--- src/wp-admin/includes/media.php	(revision 30687)
+++ src/wp-admin/includes/media.php	(working copy)
@@ -957,13 +957,14 @@
 	 *
 	 * @param array $size_names Array of image sizes and their names. Default values
 	 *                          include 'Thumbnail', 'Medium', 'Large', 'Full Size'.
+	 * @param string $context A named context of this filter.
 	 */
 	$size_names = apply_filters( 'image_size_names_choose', array(
 		'thumbnail' => __( 'Thumbnail' ),
 		'medium'    => __( 'Medium' ),
 		'large'     => __( 'Large' ),
 		'full'      => __( 'Full Size' )
-	) );
+	), __FUNCTION__ );
 
 		if ( empty($check) )
 			$check = get_user_setting('imgsize', 'medium');
Index: src/wp-includes/media-template.php
===================================================================
--- src/wp-includes/media-template.php	(revision 30687)
+++ src/wp-includes/media-template.php	(working copy)
@@ -671,11 +671,11 @@
 					<?php
 					/** This filter is documented in wp-admin/includes/media.php */
 					$sizes = apply_filters( 'image_size_names_choose', array(
-						'thumbnail' => __('Thumbnail'),
-						'medium'    => __('Medium'),
-						'large'     => __('Large'),
-						'full'      => __('Full Size'),
-					) );
+						'thumbnail' => __( 'Thumbnail' ),
+						'medium'    => __( 'Medium' ),
+						'large'     => __( 'Large' ),
+						'full'      => __( 'Full Size' ),
+					), __FUNCTION__ );
 
 					foreach ( $sizes as $value => $name ) : ?>
 						<#
@@ -750,7 +750,7 @@
 					'medium'    => __( 'Medium' ),
 					'large'     => __( 'Large' ),
 					'full'      => __( 'Full Size' ),
-				) );
+				), __FUNCTION__ );
 
 				foreach ( $size_names as $size => $label ) : ?>
 					<option value="<?php echo esc_attr( $size ); ?>">
@@ -920,11 +920,11 @@
 									<?php
 									/** This filter is documented in wp-admin/includes/media.php */
 									$sizes = apply_filters( 'image_size_names_choose', array(
-										'thumbnail' => __('Thumbnail'),
-										'medium'    => __('Medium'),
-										'large'     => __('Large'),
-										'full'      => __('Full Size'),
-									) );
+										'thumbnail' => __( 'Thumbnail' ),
+										'medium'    => __( 'Medium' ),
+										'large'     => __( 'Large' ),
+										'full'      => __( 'Full Size' ),
+									), __FUNCTION__ );
 
 									foreach ( $sizes as $value => $name ) : ?>
 										<#
Index: src/wp-includes/media.php
===================================================================
--- src/wp-includes/media.php	(revision 30687)
+++ src/wp-includes/media.php	(working copy)
@@ -2676,11 +2676,11 @@
 
 		/** This filter is documented in wp-admin/includes/media.php */
 		$possible_sizes = apply_filters( 'image_size_names_choose', array(
-			'thumbnail' => __('Thumbnail'),
-			'medium'    => __('Medium'),
-			'large'     => __('Large'),
-			'full'      => __('Full Size'),
-		) );
+			'thumbnail' => __( 'Thumbnail' ),
+			'medium'    => __( 'Medium' ),
+			'large'     => __( 'Large' ),
+			'full'      => __( 'Full Size' ),
+		), __FUNCTION__ );
 		unset( $possible_sizes['full'] );
 
 		// Loop through all potential sizes that may be chosen. Try to do this with some efficiency.