Switch on open to Edit Gallery with images

Instead of reopening the Media Gallery, which the Media Upload Button does,
when editing the gallery requires opening the Edit Gallery modal. Also
requires setting selection and event which translates backbone data.

Props to @georgeh, who I paired with developing

See wp.media.editor from wp-includes/js/media-views.js

blocks/library/gallery/index.js

@@ -11,16 +11,30 @@ import GalleryImage from './gallery-image';
 
 const { query } = hpq;
 
-const openMediaLibrary = () => {
+const editMediaLibrary = ( attributes, setAttributes ) => {
 	const frameConfig = {
-		title: wp.i18n.__( 'Select or Upload a media' ),
+		frame: 'post',
+		title: wp.i18n.__( 'Update Gallery media' ),
 		button: {
 			text: wp.i18n.__( 'Select' ),
 		},
 		multiple: true,
+		state: 'gallery-edit',
+		selection: new wp.media.model.Selection( attributes.images, { multiple: true } ),
 	};
 
-	wp.media( frameConfig ).open();
+	const editFrame = wp.media( frameConfig );
+	function updateFn() {
+		setAttributes( {
+			images: this.frame.state().attributes.library.models.map( ( a ) => {
+				return a.attributes;
+			} ),
+		} );
+	}
+
+	editFrame.on( 'insert', updateFn );
+	editFrame.state( 'gallery-edit' ).on( 'update', updateFn );
+	editFrame.open( 'gutenberg-gallery' );
 };
 
 /**
@@ -43,14 +57,15 @@ registerBlock( 'core/gallery', {
 	category: 'common',
 
 	attributes: {
+		// TODO: fix when loading view with existing gallery
 		images: query( 'div.blocks-gallery' ),
 	},
 
 	controls: [
 		{
 			icon: 'format-image',
 			title: wp.i18n.__( 'Edit Gallery' ),
-			onClick: () => openMediaLibrary(),
+			onClick: editMediaLibrary,
 		},
 		{
 			icon: 'align-left',