Adding a space when encoding ids starting with digits

escapeCss() references the following:
https://drafts.csswg.org/cssom/#serialize-an-identifier

> To escape a character as code point means to create a string of "\"
> (U+005C), followed by the Unicode code point as the smallest possible
> number of hexadecimal digits in the range 0-9 a-f (U+0030 to U+0039 and
> U+0061 to U+0066) to represent the code point in base 16, *followed by a
> single SPACE (U+0020).*

Currently the digit is being encoded, but no SPACE is being added.

Adding the SPACE.

Signed-off-by: Bob Baron <rdbaron@gmail.com>
Signed-off-by: Jason Leyba <jmleyba@gmail.com>

javascript/node/selenium-webdriver/lib/by.js

@@ -84,7 +84,7 @@ function escapeCss(css) {
         || (i == 0 && c >= 0x0030 && c <= 0x0039)
         || (i == 1 && c >= 0x0030 && c <= 0x0039
             && css.charCodeAt(0) == 0x002D)) {
-      ret += '\\' + c.toString(16);
+      ret += '\\' + c.toString(16) + ' ';
       continue;
     }
 

javascript/node/selenium-webdriver/test/lib/by_test.js

@@ -72,6 +72,18 @@ describe('by', function() {
         assert.equal('css selector', locator.using);
         assert.equal('*[name="foo\\"bar\\""]', locator.value);
       });
+
+      it('escapes the name when it starts with a number', function() {
+        let locator = by.By.name('123foo"bar"')
+        assert.equal('css selector', locator.using);
+        assert.equal('*[name="\\31 23foo\\"bar\\""]', locator.value);
+      });
+
+      it('escapes the name when it starts with a negative number', function() {
+        let locator = by.By.name('-123foo"bar"')
+        assert.equal('css selector', locator.using);
+        assert.equal('*[name="-\\31 23foo\\"bar\\""]', locator.value);
+      });
     });
   });