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There were hundreds of tests directly under paint/invalidation, causing
little paralellism and long run time when running the directory without
--fully-parallel, and always little parallelism and long run time when
running the directory as virtual suite even with --fully-parallel.

Move some tests into subdirectories to increase parallelism. Examples:
*selection*.html => selection/
*multicol*.html => multicol/
*scroll*.html => scroll/
*table*.html => table/
*box*.html => box/
...

In addition of moving the tests:
- Relative paths in the HTML files are updated;
- Expectation files are updated;
- -expected* files are moved, including common files, platform-specific files and flag-specific files.

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_root_layer_scrolls;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: Id1498a289ee7c70716216ebdfe3e625d94bca35c
Reviewed-on: https://chromium-review.googlesource.com/766652
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#516058}