GitLab

First, extends TreeGenerator so that it can not only generate every
"shape" of tree, but it can then populate that tree with every
permutation of ignored nodes.

Then, write a new test that tries every possible tree up to a certain
size and tries every possible source and destination permutation of
ignored nodes. We call this the "fat" tree. Update the source tree into
the destination tree and capture the events fired.

Next, build the equivalent "skinny" trees - the same trees but with
the ignored nodes removed. Now convert the source skinny tree into the
destination skinny tree.

Assert that the generated events fired are the same in the fat tree as
the skinny tree. In other words, ignored nodes really are ignored and
don't affect things. (The only exception is the ignored_changed
attribute.)

Finally, check every unignored node in the fat tree and make sure that its
unignored parent, children, siblings, and index in parent are all
consistent with the equivalent values in the skinny tree.

This test uncovered bugs, which were fixed in http://crrev.com/c/2125235
before this patch was uploaded for review.

Bug: 1065144
Change-Id: I82f9b3487485f1024ee066b82c23ab0cd7b60e38
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2139082Reviewed-by: Adam Ettenberger <Adam.Ettenberger@microsoft.com>
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757989}