* Update the pre-built ICU data files for all platforms

  source/data/in/icudtl.dat for non-Android platforms
  {linux,mac}/icudt*.S for linux/mac
  android/icudtl.dat and android/icudt*.S for Android
  windows/icudt.dll for Windows

* Update Android data trimming script

  1. Make sure that 'default' calendar is kept in locales where it's relevant
    : root, th, fa, ar_SA, etc.
  2. Add a minimal region data to work around a bug in ICU with pool.res
     handling

* Update gn and gyp files
* And add a TODO comment to update.sh to automate the build file update.
* Add it_CH to the locale list.
* Add sr_Latn to unit/reslocal.mk (required by sh) and
  line_normal_fi to brkitr/brklocal.mk (referred to in brkitr/fi.txt) in
  place of line_fi.

* Update and add scripts for data building
* Completely rewrite README.chromium
* Check-in the prebuilt ICU data files/assembly sources for
  Linux,Mac,Windows,Chrome OS and Android.

BUG=575007
TEST=Blink layout tests, webkit unittests
TEST=All bots can build successfully
TEST=net_unittests --gtest_filter="*ilenameUtil*"
TEST=net_unittests --gtest_filter="*IDN*" (pending bug 336973)
TEST=base_unittests --gtest_filter="*Conv*"
TEST=browser_tests --gtest_filter="*ncoding*"
TEST=base_unittests --gtest_filter="*essage*"
TEST=ui_base_unittests --gtest_filter="*ormat*"
TEST=ui_base_unittests --gtest_filter="L10n*"
R=mark@chromium.org

Review URL: https://codereview.chromium.org/1639543006 .

* Big5 : https://www.w3.org/Bugs/Public/show_bug.cgi?id=27878

  Special case the following four more code points in
  addition to U+5341, U+5345 that are already special cased.

      U+2550, U+255E, U+2561, U+256A

  For those 6 code points, the last pointer instead of the first pointer
  in index-big5.txt is used for round-trip. The first pointer is for
  decoding-only.

* KOI8-U ( https://www.w3.org/Bugs/Public/show_bug.cgi?id=17053 )

  - 0xAE and 0xBE are mapped to U+04[50]E instead of U+255[DC].
  - Add an alias KOI8-RU

BUG=544228
TEST=1. http://goo.gl/reGQPU :  encoding(form) test
 2. Layout test: fast/encoding/*

R=jsbell@chromium.org

Review URL: https://codereview.chromium.org/1514253003 .

1. Update ucmlocal.mk and convertrs.txt to refer to euc-kr-html.ucm
instead of windows-949.ucm

2. Tighten up the valid code range for the following converters:

   EUC-KR, Shift_JIS, Big5

This is to add back an ASCII range byte to the stream per
the encoding spec when they're either illegal as a 'trail byte' or
there's no assigned code point for a "lead + trail" sequence.
For instance, with this change, '0xF3 0x41' in EUC-KR is converted to
'U+FFFD U+0041' instead of 'U+FFFD'.

This change requires adding 2 ~ 8 new states to the conversion
table of each converter mentioned above leading to 6.5kB net increase
in the final data size.

3. Tighten the trail byte range for 2-byte sequences starting with 0x8E
from [A1,E2] to [A1,DF] in EUC-JP and update the corresponding generating
script.

4. Change the substitution characters for EUC-JP and Shift_JIS to
match other converters. i.e. make them produce U+FFFD when encountering
an invalid input. Before this chaange, they emitted U+001A.

5. Enable 'U_CHARSET_IS_UTF8' configuration flag.
Chromium/Blink does not rely on ICU for the code conversion between
the 'system native encoding' (if it's one of legacy encodings)
and Unicode. With this configuration, we can cut down the code size
a bit.

6. Update the icudtl.dat (all platforms) and assembly files (mac,linux)
   and the icudata dll (windows)

See https://codereview.chromium.org/1026453002 for a new blink test
added ( fast/encoding/char-decoding-invalid-trail.html )

BUG=450312,430823
TEST=Blink: fast/encoding/char-decoding-{truncated,invalid-trail}.html
TEST=base_unittests --gtest_filter=*Conv*, browser_tests --gtest_filter=*ncoding*
R=jsbell@chromium.org, mark@chromium.org

Review URL: https://codereview.chromium.org/984233002

A. Converter update per HTML encoding spec along with changes in
  the encoding name alias table.
B. Remove all the codes for converters Blink and Chromium do not need
(SCSU, Lotus, ISO-2022-xx other than JP, BOCU, UTF-7, etc).

This is reapplying the following CLs (that we used for ICU 52.1) to ICU 54.1 :

https://codereview.chromium.org/598383002
https://codereview.chromium.org/654153002

We have two upstream bugs filed for A and B above:
  http://www.icu-project.org/trac/ticket/11296
  http://www.icu-project.org/trac/ticket/10303

In addiition to A and B, we unified Big5 and Big5-HKSCS per
the encoding spec (bug 277868). That also includes properly supporting
the four 2-character sequences ( see http://crbug.com/277868#c3 ).
big5_gen.sh deviates from the current spec to work around a bug
in the spec. (see https://www.w3.org/Bugs/Public/show_bug.cgi?id=27878)

Moreover, ucmlocal.mk is added to list only encodings we want to support.

Also, tighten the state table for windows-946-2000.ucm that we use
for EUC-KR for now. And, drop 'base' map for windows-{936,949}-2000.ucm.

Finally, add euc-kr-html.ucm along with scripts/euckr_gen.sh, but
it is not yet used pending the resolution of bug 450312.

Data size checkpoint: 20,566,864 bytes (the original ICU 54=25,343,024)

BUG=277868, 428145, 450312
TEST=net_unittests --gtest_filter="*ilenameUtil*"
TEST=base_unittests --gtest_filter="*Conv*"
TEST=browser_tests --gtest_filter="*ncoding*"
TEST=Blink: fast/encoding/*
R=jsbell@chromium.org, mark@chromium.org

Review URL: https://codereview.chromium.org/839713003