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This is a reland of CL:
https://chromium-review.googlesource.com/c/chromium/src/+/1014464
which was reverted by:
https://chromium-review.googlesource.com/c/chromium/src/+/1043187
due to compilation error.

Original commit message:
> Refactor AXSnapshotNodeAndroid into mojo.
>
> Test: browser_tests --gtest_filter=ArcVoiceInteractionArcHomeServiceTest.*
TBR=dmazzoni@chromium.org,sky@chromium.org,dcheng@chromium.org

Change-Id: Ieca4bf35f3aa913683e8d1ce34160731317a797f
Reviewed-on: https://chromium-review.googlesource.com/1045487Reviewed-by: Muyuan Li <muyuanli@chromium.org>
Commit-Queue: Muyuan Li <muyuanli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556983}