[x/tour] go-tour: show lines highlighted with present's "// HLfoo" feature

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/13253051
X-Tour-Commit: a77b609bb84a8d86ff1de4b02736e1013a336360

tour/js/tour.js

@@ -200,7 +200,23 @@ function show(i) {
 		$('#wrap').removeClass('full-width');
 		$('#workspace').show();
 		$output.empty();
-		editor.setValue(load(i) || $s.find('div.source').text().trim());
+
+		// Load stored code from HTML source or from the pageData cache.
+		// Highlight "HL" lines if the cached data hasn't been changed.
+		var $src = $s.find('div.source');
+		var orig = $src.text().trim();
+		var loaded = load(i);
+		if (loaded && loaded != orig) {
+			editor.setValue(loaded); 
+		} else {
+			editor.setValue(orig); 
+			$src.find('b').closest('span').each(function() {
+				var n = $(this).attr('num')*1 - 1;
+				editor.setLineClass(n, null, 'highlightLine');
+			});
+			clearHighlightOnChange();
+		}
+
 		editor.focus();
 	}
 
@@ -342,6 +358,10 @@ function highlightErrors(text) {
 		var line = result[1]*1-1;
 		editor.setLineClass(line, null, 'errLine');
 	}
+	clearHighlightOnChange();
+}
+
+function clearHighlightOnChange() {
 	editor.setOption('onChange', function() {
 		for (var i = 0; i < editor.lineCount(); i++) {
 			editor.setLineClass(i, null, null);

tour/static/tour.css

@@ -229,6 +229,9 @@ div.source {
 .CodeMirror .errLine {
 	background: #FDD !important;
 }
+.CodeMirror .highlightLine {
+	background: #E0EBF5 !important;
+}
 
 #slides pre {
 	background: #E9E9E9;