CSS escape doesn't escape leading hyphen.

LayoutTests/css3/escape-dom-api.html

Index: LayoutTests/css3/escape-dom-api.html
diff --git a/LayoutTests/css3/escape-dom-api.html b/LayoutTests/css3/escape-dom-api.html
index b4cbfe6cd8517d718260bc47cf3c457976a70437..e2e358397f1abf9293d578a93a6f5b0d35831dfd 100644
--- a/LayoutTests/css3/escape-dom-api.html
+++ b/LayoutTests/css3/escape-dom-api.html
@@ -54,6 +54,8 @@
     shouldBeEqualToString("CSS.escape('-8a')", "-\\38 a");
     shouldBeEqualToString("CSS.escape('-9a')", "-\\39 a");
 
+    shouldBeEqualToString("CSS.escape('-')", "\\-");

[mathias, 2015/09/10 10:13:04]

To match the updated source tests, add this:

    shouldBeEqualToString("CSS.escape('-a')", "-a");

See
https://github.com/mathiasbynens/CSS.escape/blob/a936627f36f58a271a11eb295896...

+    shouldBeEqualToString("CSS.escape('--')", "--");

[mathias, 2015/09/10 10:20:25]

This test expectation is incorrect. It should be `-\\-`.

See the spec: “If the character is the second character and is a `-` (U+002D),
and the first character is also a `-` (U+002D), and there is no third character,
[…]”

     shouldBeEqualToString("CSS.escape('--a')", "--a");
 
     shouldBeEqualToString("CSS.escape('\x80\x2D\x5F\xA9')", "\x80\x2D\x5F\xA9");