The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/92891e6490067594b96b74637bbede51f6f52234

commit 92891e6490067594b96b74637bbede51f6f52234
Author: Dominik Röttsches <drott@chromium.org>
Date: Mon Nov 06 14:57:01 2017

Let SymbolsIterator pass through Emoji subdivision flags

This lets tag sequences as defined in UTR#51 [1] pass through important
parts of our text stack, the CachingWordShapeIterator as well as the
RunSegmenter/SymbolsIterator combination. We currently do not make any
attempts at filtering or validating tag sequences or restricting their
size to 32 characters, as UTR#51 suggests. The flag lookup is left to
the OpenType features of the Emoji font.

[1] http://www.unicode.org/reports/tr51/proposed.html#flag-emoji-tag-sequences

Test: EmojiSubdivisionFlags in RunSegmenterTest, SymbolsIteratorTest and CachingWordShaperTest
Bug:  719965 
Change-Id: I37452ed2ee8fa2e4485ea3eb0186596262d5a2b2
Reviewed-on: https://chromium-review.googlesource.com/754835
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/master@{#514126}
[modify] https://crrev.com/92891e6490067594b96b74637bbede51f6f52234/third_party/WebKit/Source/platform/fonts/SymbolsIterator.cpp
[modify] https://crrev.com/92891e6490067594b96b74637bbede51f6f52234/third_party/WebKit/Source/platform/fonts/SymbolsIteratorTest.cpp
[modify] https://crrev.com/92891e6490067594b96b74637bbede51f6f52234/third_party/WebKit/Source/platform/fonts/shaping/CachingWordShapeIterator.h
[modify] https://crrev.com/92891e6490067594b96b74637bbede51f6f52234/third_party/WebKit/Source/platform/fonts/shaping/CachingWordShaperTest.cpp
[modify] https://crrev.com/92891e6490067594b96b74637bbede51f6f52234/third_party/WebKit/Source/platform/fonts/shaping/RunSegmenterTest.cpp
[modify] https://crrev.com/92891e6490067594b96b74637bbede51f6f52234/third_party/WebKit/Source/platform/text/Character.cpp
[modify] https://crrev.com/92891e6490067594b96b74637bbede51f6f52234/third_party/WebKit/Source/platform/text/Character.h
[modify] https://crrev.com/92891e6490067594b96b74637bbede51f6f52234/third_party/WebKit/Source/platform/wtf/text/CharacterNames.h