HasRTLChars() appears in profile of attachment 8848015 after landing the patches
for bug 1391538 because the landing made text in <input> or <textarea> always
treated as non-single byte characters. Therefore, HasRTLChars() is now called
by nsTextFragment::SetTo() a lot in editors.
HasRTLChar() checks if it's in an RTL character for each character until it
becomes true. However, if character is less than the minimum RTL character,
U+0590, it works faster at least for Western languages.
MozReview-Commit-ID: 4YecxQWUcmK
--HG--
extra : rebase_source : 172be670795f0e2155d4bd5044ee37f652367734
6b9eda1dda