Revert "Remove perf_expectations"

This reverts commit 9d5ef42ab6f3967d19dd687740645ad2fec66ccd.

Reason for revert: See crbug.com/893254; looks like a typo in the script.

Original change's description:
> Remove perf_expectations
> 
> This is a modified reland of [1] with most of the changes to sizes.py reverted.
> Those changes are still used by the perf dashboard so must be kept around for
> the time being.
> 
> [1] https://chromium.googlesource.com/chromium/src.git/+/5f552b39961e3b36e018fdd7d3d452526bde2e4f
> 
> R=​dpranke
> Bug: 572393
> Cq-Include-Trybots: luci.chromium.try:linux_chromium_archive_rel_ng;luci.chromium.try:mac_chromium_archive_rel_ng;luci.chromium.try:win_archive;luci.chromium.try:win_x64_archive;master.tryserver.chromium.android:android_archive_rel_ng
> 
> Change-Id: I459387d50f4a328192110c7b75983523a14f787d
> Reviewed-on: https://chromium-review.googlesource.com/c/1255303
> Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
> Reviewed-by: Dirk Pranke <dpranke@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#597614}

TBR=thakis@chromium.org,dpranke@chromium.org,thomasanderson@chromium.org

Change-Id: Ife13ece23ed3513225003bd18fbe27b0bbf16afc
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 572393
Cq-Include-Trybots: luci.chromium.try:linux_chromium_archive_rel_ng;luci.chromium.try:mac_chromium_archive_rel_ng;luci.chromium.try:win_archive;luci.chromium.try:win_x64_archive;master.tryserver.chromium.android:android_archive_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/c/1268904
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#597633}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: a230a9900389fef6bc948cf69b1c8d37836f3359
10 files changed