exp/template/html: fix bug /*/ is not a full JS block comment.

Similar tests for CSS already catch this problem in tCSS.

R=nigeltao
CC=golang-dev
https://golang.org/cl/4967065

src/pkg/exp/template/html/escape.go

@@ -487,9 +487,9 @@ func tJS(c context, s []byte) (context, []byte) {
 	case '/':
 		switch {
 		case i+1 < len(s) && s[i+1] == '/':
-			c.state = stateJSLineCmt
+			c.state, i = stateJSLineCmt, i+1
 		case i+1 < len(s) && s[i+1] == '*':
-			c.state = stateJSBlockCmt
+			c.state, i = stateJSBlockCmt, i+1
 		case c.jsCtx == jsCtxRegexp:
 			c.state = stateJSRegexp
 		default:

src/pkg/exp/template/html/escape_test.go

@@ -643,6 +643,14 @@ func TestEscapeText(t *testing.T) {
 			`<a onclick="/*`,
 			context{state: stateJSBlockCmt, delim: delimDoubleQuote},
 		},
+		{
+			`<a onclick="/*/`,
+			context{state: stateJSBlockCmt, delim: delimDoubleQuote},
+		},
+		{
+			`<a onclick="/**/`,
+			context{state: stateJS, delim: delimDoubleQuote},
+		},
 		{
 			`<a onkeypress="&quot;`,
 			context{state: stateJSDqStr, delim: delimDoubleQuote},