Omit chromium-luci in rolls when not changed

Updates the Chromium -> Dawn roller script to omit the chromium-luci
repo from the list of changed repos if there were no actual changes.

Bug: 459517292
Change-Id: I18ccfa32ffb584d9b73d9fa1db0535d64b52a058
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/290935
Auto-Submit: Brian Sheedy <bsheedy@google.com>
Reviewed-by: Jonathan Lee <jonathanjlee@google.com>
Commit-Queue: Jonathan Lee <jonathanjlee@google.com>
Commit-Queue: Brian Sheedy <bsheedy@google.com>

scripts/roll_chromium_deps.py

diff --git a/scripts/roll_chromium_deps.py b/scripts/roll_chromium_deps.py
index e3b8653..20a626e 100755
--- a/scripts/roll_chromium_deps.py
+++ b/scripts/roll_chromium_deps.py
@@ -1100,10 +1100,14 @@
 
     # We want this entry to be in the commit message, but we do not want it to
     # be present for _apply_changed_deps() since it is not actually a DEPS
-    # entry.
+    # entry. We also don't want it to be present if no actual changes occurred.
     chromium_luci_entry = _sync_chromium_luci_revision(
         revision_range.new_revision)
-    entries_for_commit_message = changed_entries + [chromium_luci_entry]
+    entries_for_commit_message = changed_entries
+    if chromium_luci_entry.old_revision != chromium_luci_entry.new_revision:
+        entries_for_commit_message = entries_for_commit_message + [
+            chromium_luci_entry
+        ]
 
     # Create the commit message before adding the entry for the Chromium
     # revision since Chromium information is explicitly added to the message.