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There are no order guarantees in the remote updates received from
the server.
However, for hierarchical types such as bookmarks, it's important
to process updates in the correct order.
For example parent node creation should happen before child node
creation.

This CL implements the following reordering rules for bookmark
remote updates in USS.
1. Creations and updates come before deletions.
2. Parent creation/update should come before child creation/update.
3. No need to further order deletions. Parent deletions can
   happen before child deletions. This is safe because all updates
   (e.g. moves) should have been processed already.

Bug: 516866
Change-Id: I059224b897ea51a4a0321124b082e76be824d28f
Reviewed-on: https://chromium-review.googlesource.com/1141870
Commit-Queue: Mohamed Amir Yosef <mamir@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577232}