Revert "Update to the latest package:csslib"

This reverts commit 486e867093e913d04fb8384d235c84a24cbfb556.

Reason for revert: Breaks google3 code. Will do selective
reverts upstream before rolling again.

Original change's description:
> Update to the latest package:csslib
>
> Change-Id: Iedf84af1a7f5d454b8d9b2e56a8e91fdfe84e952
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/222260
> Auto-Submit: Nate Bosch <nbosch@google.com>
> Commit-Queue: Nate Bosch <nbosch@google.com>
> Commit-Queue: Leon Senft <leonsenft@google.com>
> Reviewed-by: Leon Senft <leonsenft@google.com>

TBR=nbosch@google.com,leonsenft@google.com

Change-Id: I46fde47be272c07e0dc129656fd3f93f55e979e0
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/222320
Reviewed-by: Nate Bosch <nbosch@google.com>
Commit-Queue: Nate Bosch <nbosch@google.com>
diff --git a/DEPS b/DEPS
index 223252f..4925dd5 100644
--- a/DEPS
+++ b/DEPS
@@ -91,7 +91,7 @@
   "collection_rev": "a4c941ab94044d118b2086a3f261c30377604127",
   "convert_rev": "e063fdca4bebffecbb5e6aa5525995120982d9ce",
   "crypto_rev": "b5024e4de2b1c474dd558bef593ddbf0bfade152",
-  "csslib_rev": "6fc1c302467a7812f161842e1c4b757c17c1fa82",
+  "csslib_rev": "02abc1ddf93092efef2be365300f15504d23cd23",
 
   # Note: Updates to dart_style have to be coordinated with the infrastructure
   # team so that the internal formatter `tools/sdks/dart-sdk/bin/dart format`