avoid multiple charAt calls for injectedLogSite equals()

[copybara-service]

avoid multiple charAt calls for injectedLogSite equals()

RELNOTES=n/a

[hagbard]

Since '.' == 2E and '/' == 2F, the test can be rewritten from:

        if (c1 != c2) {
          // If the characters are not equal, but the slash/dot difference is accounted for, then
          // consider them equivalent.
          if (!(c1 == '/' && c2 == '.') && !(c1 == '.' && c2 == '/')) {
            return false;
          }
        }

To:

        if (c1 != c2) {
          // Account for '.' (0x2E) and '/' (0x2F) being equivalent by using the fact they differ only in the lowest bit.
          if ((c1 & ~0x1) != 0x2E || (c1 ^ c2) != 0x1) {
            return false;
        }

And in the latter form the failure case if likely to be hit after a simpler test.