ash: Allow StopDataCollection without starting

CUJ recorder force stop frame tracking to ensure test cases do
not interfere each other in http://crrev.com/c/4685262. Stop
without starting is a valid case now and the DHCECK is causing
problems when running CUJ with a dcheck enabled chrome.

Bug: b:268541084
Change-Id: I5f1efc01d9ade7d288777e7af6c7d5ab34a1ea35
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4939517
Commit-Queue: Achuith Bhandarkar <achuith@chromium.org>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1209782}

ash/public/cpp/metrics_util.cc

@@ -119,7 +119,6 @@ void StartDataCollection() {
 }
 
 std::vector<AnimationData> StopDataCollection() {
-  DCHECK(g_data_collection_enabled);
   g_data_collection_enabled = false;
 
   return GetCollectedData();