Revert "Normalize Katakana to Hiragana in ScriptRunIterator"

This reverts commit 05672d8d.

Reason for revert: Test failures https://bugs.chromium.org/p/chromium/issues/detail?id=906587

Original change's description:
> Normalize Katakana to Hiragana in ScriptRunIterator
> 
> This patch normalizes Katakana to Hiragana in ScriptData, and
> thus in ScriptRunIterator.
> 
> There are 3 ICU script code for kana; USCRIPT_HIRAGANA,
> USCRIPT_KATAKANA, and USCRIPT_KATAKANA_OR_HIRAGANA. However,
> OpenType has only one 'kana' for all these 3 script codes.
> 
> When shaping, HarfBuzz handles the normalization. However,
> Blink splits the incoming string by the ICU scripts.
> Splitting these 3 scripts is not useful but consumes CPU
> and memory.
> 
> By normalizing in ScriptRunIterator, all types of Kana are
> in single run.
> 
> timeToFirstContentfulPaint:layout shows ~3% improvements
> https://pinpoint-dot-chromeperf.appspot.com/job/10d9760fe40000
> 
> though bink_perf.layout does not show much differences
> https://pinpoint-dot-chromeperf.appspot.com/job/14f19c00140000
> 
> This is probably because Katakana characters are not used
> much in `japanese-kokoro-insert` (written in ~100 years ago,)
> while they are more used in modern pages.
> 
> Bug: 636993
> Change-Id: If692bb575f2232b8fca10cd2ea87e3022debdf05
> Reviewed-on: https://chromium-review.googlesource.com/c/1337650
> Commit-Queue: Koji Ishii <kojii@chromium.org>
> Reviewed-by: Dominik Röttsches <drott@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#609119}

TBR=eae@chromium.org,kojii@chromium.org,drott@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 636993
Change-Id: Icb14d6ad2a3453c9bfab9287e5c0a4995ac1c97f
Reviewed-on: https://chromium-review.googlesource.com/c/1341519Reviewed-by: Maxim Kolosovskiy <kolos@chromium.org>
Commit-Queue: Maxim Kolosovskiy <kolos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609266}

third_party/blink/renderer/platform/fonts/script_run_iterator.cc

@@ -10,26 +10,6 @@
 
 namespace blink {
 
-namespace {
-
-// UScriptCode and OpenType script are not 1:1; specifically, both Hiragana and
-// Katakana map to 'kana' in OpenType. They will be mapped correctly in
-// HarfBuzz, but normalizing earlier helps to reduce splitting runs between
-// these scripts.
-// https://docs.microsoft.com/en-us/typography/opentype/spec/scripttags
-inline UScriptCode getScriptForOpenType(UChar32 ch, UErrorCode* status) {
-  UScriptCode script = uscript_getScript(ch, status);
-  if (UNLIKELY(U_FAILURE(*status)))
-    return script;
-  if (UNLIKELY(script == USCRIPT_KATAKANA ||
-               script == USCRIPT_KATAKANA_OR_HIRAGANA)) {
-    return USCRIPT_HIRAGANA;
-  }
-  return script;
-}
-
-}  // namespace
-
 typedef ScriptData::PairedBracketType PairedBracketType;
 
 constexpr int ScriptRunIterator::kMaxScriptCount;
@@ -47,10 +27,6 @@ void ICUScriptData::GetScripts(UChar32 ch, UScriptCodeList& dst) const {
   // regardless of the capacity passed to the call. So count can be greater
   // than dst->size(), if a later version of the unicode data has more
   // than kMaxScriptCount items.
-
-  // |uscript_getScriptExtensions| do not need to be collated to
-  // USCRIPT_HIRAGANA because when ScriptExtensions contains Kana, it contains
-  // Hira as well, and Hira is always before Kana.
   int count = uscript_getScriptExtensions(ch, &dst[0], dst.size(), &status);
   if (status == U_BUFFER_OVERFLOW_ERROR) {
     // Allow this, we'll just use what we have.
@@ -59,7 +35,7 @@ void ICUScriptData::GetScripts(UChar32 ch, UScriptCodeList& dst) const {
     count = dst.size();
     status = U_ZERO_ERROR;
   }
-  UScriptCode primary_script = getScriptForOpenType(ch, &status);
+  UScriptCode primary_script = uscript_getScript(ch, &status);
 
   if (U_FAILURE(status)) {
     DLOG(ERROR) << "Could not get icu script data: " << status << " for 0x"

third_party/blink/renderer/platform/fonts/script_run_iterator_test.cc

@@ -370,50 +370,6 @@ TEST_F(ScriptRunIteratorTest, Chinese) {
   CHECK_SCRIPT_RUNS({{"萬國碼", USCRIPT_HAN}});
 }
 
-struct JapaneseMixedScript {
-  const char* string;
-  // The expected primary_script when the string alone was evaluated.
-  UScriptCode script;
-} japanese_mixed_scripts[] = {{"あ", USCRIPT_HIRAGANA},
-                              // Katakana should be normalized to Hiragana
-                              {"ア", USCRIPT_HIRAGANA},
-                              // Script_Extensions=Hira Kana
-                              {"\u30FC", USCRIPT_HIRAGANA},
-                              // Script_Extensions=Hani Hira Kana
-                              {"\u303C", USCRIPT_HAN},
-                              // Script_Extensions=Bopo Hang Hani Hira Kana
-                              {"\u3003", USCRIPT_BOPOMOFO},
-                              // Script_Extensions=Bopo Hang Hani Hira Kana Yiii
-                              {"\u3001", USCRIPT_BOPOMOFO}};
-
-class JapaneseMixedScriptTest
-    : public ScriptRunIteratorTest,
-      public testing::WithParamInterface<JapaneseMixedScript> {};
-
-INSTANTIATE_TEST_CASE_P(ScriptRunIteratorTest,
-                        JapaneseMixedScriptTest,
-                        testing::ValuesIn(japanese_mixed_scripts));
-
-TEST_P(JapaneseMixedScriptTest, Data) {
-  const auto& data = GetParam();
-  std::string string(data.string);
-
-  CheckRuns({{string.data(), data.script}});
-
-  // If the string follows Hiragana or Katakana, or is followed by Hiragnaa or
-  // Katakana, it should be normalized as Hiragana.
-  std::string hiragana("か");
-  std::string katakana("カ");
-  CheckRuns({{(hiragana + string).data(), USCRIPT_HIRAGANA}});
-  CheckRuns({{(string + hiragana).data(), USCRIPT_HIRAGANA}});
-
-  CheckRuns({{(katakana + string).data(), USCRIPT_HIRAGANA}});
-  CheckRuns({{(string + katakana).data(), USCRIPT_HIRAGANA}});
-
-  CheckRuns({{(hiragana + string + katakana).data(), USCRIPT_HIRAGANA}});
-  CheckRuns({{(katakana + string + hiragana).data(), USCRIPT_HIRAGANA}});
-}
-
 // Close bracket without matching open is ignored
 TEST_F(ScriptRunIteratorTest, UnbalancedParens1) {
   CHECK_SCRIPT_RUNS(