Editor: When stripping paragraph tags, and there is a <br> at the beginning or the end, merge them and keep the paragraph, not the <br>.

Props rellect.
Fixes #37066.
Built from https://develop.svn.wordpress.org/trunk@40787


git-svn-id: http://core.svn.wordpress.org/trunk@40645 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/js/editor.js

@@ -224,8 +224,14 @@ window.wp = window.wp || {};
 			// Normalize white space chars and remove multiple line breaks.
 			html = html.replace( /\n[\s\u00a0]+\n/g, '\n\n' );
 
-			// Rrplace <br> tags with a line break.
-			html = html.replace( /\s*<br ?\/?>\s*/gi, '\n' );
+			// Replace <br> tags with line breaks.
+			html = html.replace( /(\s*)<br ?\/?>\s*/gi, function( match, space ) {
+				if ( space && space.indexOf( '\n' ) !== -1 ) {
+					return '\n\n';
+				}
+
+				return '\n';
+			});
 
 			// Fix line breaks around <div>.
 			html = html.replace( /\s*<div/g, '\n<div' );

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.8-beta1-40786';
+$wp_version = '4.8-beta1-40787';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.