update chrome-icu 102

Author: jinqiang zhang

project-cros-pi/chromeos-base/chrome-icu/OWNERS

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+chromeos-ci-prod@chromeos-bot.iam.gserviceaccount.com

project-cros-pi/chromeos-base/chrome-icu/README.md

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+# The Chrome ICU package
+
+This ebuild builds and installs the [icu package in chrome][chrome-icu-location]
+so that it can be used in Chrome OS. Compared with the vanilla ICU library, it
+is customised for Chrome so there are some missing functionality and encoding
+(e.g. ISO-2022-CN and ISO-2022-KR). But it should be powerful enough for most
+usages. (It supports the i18n of Chrome!)
+
+[TOC]
+
+## Why chrome-icu?
+
+The biggest reason is to save resources. Chrome-icu saves,
+
+1.  10MB of rootfs disk space due to sharing the icu data.
+2.  Up to 10MB of RAM because of sharing the icu data.
+3.  Maintaining effort in Chrome OS (icu needs regular major uprev every 6
+    months and small bug fixes from time to time).
+
+## How to use it?
+
+> Please give us a heads-up if you want to use it. This is because chrome-icu
+> is currently a static library, so linking it will non-trivially increase the
+> disk space. And if the users of chrome-icu become more and more, we will
+> spend the effort to make it into a shared library. (This will not affect your
+> usage, please see [the tracker][make-into-shared-library].)
+
+1.  Add `chrome-icu` as a dependency in your ebuild.
+2.  Link `icui18n-chrome` and `icuuc-chrome` libraries.
+3.  Add header paths `${sysroot}/usr/include/icu-chrome/common` and
+    `${sysroot}/usr/include/icu-chrome/i18n`.
+4.  If some headers are missing, you can add them to [here][chrome-icu-headers].
+5.  At run time, load the icu data file from `/opt/google/chrome/icudtl.dat`.
+    You can follow the example [here][ml-service-load-icu-data].
+
+## TODO
+
+1.  We should consider
+    [setting up a CQ tryjob for chrome-icu][chrome-side-tryjob-tracker],
+    although this has become not very urgent after we
+    [only configure the icu package][cl-that-only-configure-icu] in compiling
+    chrome-icu.
+2.  We should consider having a `build-chrome.eclass` and avoid the duplication
+    between `chromeos-chrome.ebuild` and `chrome-icu.ebuild`. (We used to
+    duplicate the code because chrome-icu used to be very experimental so we do
+    not want to greatly change the `chromeos-chrome.ebuild` for it. With
+    chrome-icu method becoming stable, we can consider it now.)
+
+## Other questions
+
+### Emerging chrome-icu in cros chroot takes ages. What happened and how to resolve it?
+
+This normally means that there is no prebuilt binary available for chrome-icu
+so it has to build chrome-icu from source and this needs the whole chrome repo.
+Because chrome-icu and chrome share a similar build mechanism, this usually
+implies that there is no prebuilt binary available for chrome too. So if you
+just did a repo sync and found it has to build chrome-icu from source in running
+`build_packages`, it means you will also need to build chrome from source too
+--- it is only because chrome depends on chrome-icu so the latter will be built
+first.
+
+How to resolve it: There are a few methods that you could try,
+
+1.  Run `emerge-$BOARD -G chrome-icu` and see if this succeeds and
+    satisfies your needs. (This command enforce emerging chrome-icu from
+    prebuilt binary.)
+2.  If this is because the repo synced is very fresh, consider syncing to an
+    older version of Chrome OS (e.g. [sync to green][sync-to-green]).
+3.  If this is caused by changing configurations (e.g. USE flag changes), you
+    could let chrome-icu built from your local chrome checkout. First, you
+    need to enter your chroot with the `--chrome-root` option pointing to your
+    local chrome checkout. Then after entering the chroot, the chrome checkout
+    is located at "~/chrome_root". Second, now you can run
+    `CHROME_ORIGIN=LOCAL_SOURCE emerge-$BOARD chrome-icu` to build it form
+    local chrome checkout.
+
+### Why is chrome-icu a static library, not a shared library?
+
+This is because: First, making it into a static library is easier and
+requires less modifications in chrome; Second, currently only two packages
+are using it, and total size increase of linking it statically is smaller
+than that of making it into a shared library.
+
+### After we make chrome-icu into a shared library, can chrome use it too to save more disk space?
+
+The answer is no. This is because in chrome, icu is compiled with
+"control-flow integrity (CFI)" turned on. And CFI currently does not work
+well with shared libraries.
+
+### I want to use the chrome-icu mechanism to share other code in Chrome with Chrome OS. How should I do this?
+
+Theoretically, the method used by chrome-icu should be able to share any
+code in chrome to Chrome OS. But considering that 1) the chrome-icu method
+is still very new and 2) it requires changes in both chrome and the infra
+configurations, we recommend you to first chat with the Chrome OS build team
+to discuss about your problem before moving forward. And there are other
+(e.g. more lightweight) [sharing methods](http://go/chromeos-code-sharing) which
+may be more suitable.
+
+
+[chrome-side-tryjob-tracker]: https://crbug.com/1133101
+[cl-that-only-configure-icu]: https://crrev.com/c/2524460
+[sync-to-green]: https://chromium.googlesource.com/chromiumos/docs/+/HEAD/developer_guide.md#sync-to-green
+[make-into-shared-library]: https://crbug.com/1152936
+[chrome-icu-headers]: https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/HEAD/chromeos-base/chrome-icu/chrome-icu-9999.ebuild#629
+[ml-service-load-icu-data]: https://chromium.googlesource.com/chromiumos/platform2/+/HEAD/ml/machine_learning_service_impl.cc#75
+[chrome-icu-location]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/icu/