Compat: Make roller deal with compat expectations

This CL changes these tools so instead of passing around
a list of results they pass around map of lists of results
where the key of the map is "core" or "compat".

Change-Id: I3b64b5cc9a1b637eb4fe2f971691c5abdf2cb9a4
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/157561
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
diff --git a/tools/src/cmd/cts/roll/roll_test.go b/tools/src/cmd/cts/roll/roll_test.go
index 800d9ff..552509b 100644
--- a/tools/src/cmd/cts/roll/roll_test.go
+++ b/tools/src/cmd/cts/roll/roll_test.go
@@ -73,6 +73,7 @@
 
 Regenerated:
  - expectations.txt
+ - compat-expectations.txt
  - ts_sources.txt
  - test_list.txt
  - cache_list.txt