Block U+0620 on Mac from being shown in Unicode in IDN

Mac OS UI fonts renders U+0620 as blank. (radar/32458012)

Bug: chromium:725660
Test: components_unittests --gtest_filter=*IDNToUni*
Change-Id: Ib7d678aae0379e8ac53064663660a7840e5fd3bd
Reviewed-on: https://chromium-review.googlesource.com/517669
Commit-Queue: Jungshik Shin <jshin@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#475842}

components/url_formatter/idn_spoof_checker.cc

@@ -380,7 +380,11 @@ void IDNSpoofChecker::SetAllowedUnicodeSet(UErrorCode* status) {
 #if defined(OS_MACOSX)
   // The following characters are reported as present in the default macOS
   // system UI font, but they render as blank. Remove them from the allowed
-  // set to prevent spoofing.
+  // set to prevent spoofing until the font issue is resolved.
+
+  // Arabic letter KASHMIRI YEH. Not used in Arabic and Persian.
+  allowed_set.remove(0x0620u);
+
   // Tibetan characters used for transliteration of ancient texts:
   allowed_set.remove(0x0F8Cu);
   allowed_set.remove(0x0F8Du);

components/url_formatter/url_formatter_unittest.cc

@@ -414,8 +414,11 @@ const IDNTestCase idn_cases[] = {
   // Hebrew Gershayim with Arabic is disallowed.
   {"xn--5eb7h.eg", L"\x0628\x05f4.eg", false},
 #if defined(OS_MACOSX)
-  // Tibetan transliteration characters are disallowed on Mac.
+  // These characters are blocked due to a font issue on Mac.
+  // Tibetan transliteration characters.
   {"xn--com-luma.test.pl", L"\u0f8c.test.pl", false},
+  // Arabic letter KASHMIRI YEH
+  {"xn--fgb.com", L"\u0620.com", false},
 #endif
 
   // Hyphens (http://unicode.org/cldr/utility/confusables.jsp?a=-)