html: parse more malformed tags.

This continues the work in revision 914a659b44ff, now passing more test
cases. As before, the new tokenization tests match html5lib's behavior.

Fixes #2124.

R=dsymonds, r
CC=golang-dev
https://golang.org/cl/4867042

src/pkg/html/token.go

@@ -429,7 +429,7 @@ loop:
 	for ; i < z.p1; i++ {
 		c := z.buf[i]
 		switch c {
-		case '<', '>', '"', '\'', '/', '=':
+		case '>', '/', '=':
 			break loop
 		}
 		switch {

src/pkg/html/token_test.go

@@ -49,14 +49,24 @@ var tokenTests = []tokenTest{
 	},
 	{
 		"malformed tag #1",
+		`<p </p>`,
+		`<p <="" p="">`,
+	},
+	{
+		"malformed tag #2",
 		`<p id=0</p>`,
 		`<p id="0&lt;/p">`,
 	},
 	{
-		"malformed tag #2",
+		"malformed tag #3",
 		`<p id="0</p>`,
 		`<p id="0&lt;/p&gt;">`,
 	},
+	{
+		"malformed tag #4",
+		`<p id="0"</p>`,
+		`<p id="0" <="" p="">`,
+	},
 	// Comments.
 	{
 		"comment0",