Revert "Normalize Katakana to Hiragana in ScriptRunIterator"

This reverts commit 05672d8d19afbbfada4f027ac1a9f27228bc78a6.

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/1341519
Reviewed-by: Maxim Kolosovskiy <kolos@chromium.org>
Commit-Queue: Maxim Kolosovskiy <kolos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609266}
2 files changed