TinyMCE: A11y: Remove title attributes and improve placeholders.

Shifts the `title` attribute on `more` and `page-break` placeholder images to `alt`, moves the `title` attribute to `alt` on the `style` and `script` placeholders and replaces the images to differentiate between CSS and JS content.

Props sabernhardt, abcd95, joedolson.
Fixes #62861.

git-svn-id: https://develop.svn.wordpress.org/trunk@60007 602fd350-edb4-49c9-b593-d223f7449a82

Author: joedolson

src/js/_enqueues/vendor/tinymce/plugins/wordpress/plugin.js

@@ -116,7 +116,7 @@ tinymce.PluginManager.add( 'wordpress', function( editor ) {
 
 				event.content = event.content.replace( /<!--more(.*?)-->/g, function( match, moretext ) {
 					return '<img src="' + tinymce.Env.transparentSrc + '" data-wp-more="more" data-wp-more-text="' + moretext + '" ' +
-						'class="wp-more-tag mce-wp-more" alt="" title="' + title + '" data-mce-resize="false" data-mce-placeholder="1" />';
+						'class="wp-more-tag mce-wp-more" alt="' + title + '" data-mce-resize="false" data-mce-placeholder="1" />';
 				});
 			}
 
@@ -125,7 +125,7 @@ tinymce.PluginManager.add( 'wordpress', function( editor ) {
 
 				event.content = event.content.replace( /<!--nextpage-->/g,
 					'<img src="' + tinymce.Env.transparentSrc + '" data-wp-more="nextpage" class="wp-more-tag mce-wp-nextpage" ' +
-						'alt="" title="' + title + '" data-mce-resize="false" data-mce-placeholder="1" />' );
+						'alt="' + title + '" data-mce-resize="false" data-mce-placeholder="1" />' );
 			}
 
 			if ( event.load && event.format !== 'raw' ) {
@@ -144,10 +144,9 @@ tinymce.PluginManager.add( 'wordpress', function( editor ) {
 						'data-wp-preserve="' + encodeURIComponent( match ) + '" ' +
 						'data-mce-resize="false" ' +
 						'data-mce-placeholder="1" '+
-						'class="mce-object" ' +
+						'class="mce-object mce-object-' + tag + '" ' +
 						'width="20" height="20" '+
 						'alt="&lt;' + tag + '&gt;" ' +
-						'title="&lt;' + tag + '&gt;" ' +
 					'/>';
 				} );
 			}
@@ -214,7 +213,7 @@ tinymce.PluginManager.add( 'wordpress', function( editor ) {
 		classname += ' mce-wp-' + tag;
 		title = tag === 'more' ? 'Read more...' : 'Next page';
 		title = __( title );
-		html = '<img src="' + tinymce.Env.transparentSrc + '" alt="" title="' + title + '" class="' + classname + '" ' +
+		html = '<img src="' + tinymce.Env.transparentSrc + '" alt="' + title + '" class="' + classname + '" ' +
 			'data-wp-more="' + tag + '" data-mce-resize="false" data-mce-placeholder="1" />';
 
 		// Most common case.

src/js/_enqueues/vendor/tinymce/skins/wordpress/images/script.svg

@@ -160,6 +160,14 @@ img[data-mce-selected]::selection {
 	background: transparent url( images/pagebreak.png ) repeat-y scroll center center;
 }
 
+.mce-object-style {
+	background-image: url( images/style.svg );
+}
+
+.mce-object-script {
+	background-image: url( images/script.svg );
+}
+
 /* Styles for formatting the boundaries of anchors and code elements */
 .mce-content-body a[data-mce-selected] {
 	padding: 0 2px;