Fix multiple CIPD dependencies in roller script

Fixes a bug in the Chromium -> Dawn roller script when rolling CIPD
dependencies with multiple packages in a single dependency. Previously,
only a single --revision flag was generated for all packages, but now
one is generated for each package.

This does not currently affect Dawn since all current Dawn CIPD
dependencies only contain a single package. However, ANGLE's equivalent
script ran into issues without this fix in place.

Change-Id: Id8642c365422d84a6a75de75c1a9a4e1f2c71ea6
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/307955
Auto-Submit: Brian Sheedy <bsheedy@google.com>
Commit-Queue: Brian Sheedy <bsheedy@google.com>
Reviewed-by: Jonathan Lee <jonathanjlee@google.com>
Commit-Queue: Jonathan Lee <jonathanjlee@google.com>

scripts/roll_chromium_deps.py

diff --git a/scripts/roll_chromium_deps.py b/scripts/roll_chromium_deps.py
index c04194a..5dbeded 100755
--- a/scripts/roll_chromium_deps.py
+++ b/scripts/roll_chromium_deps.py
@@ -37,6 +37,7 @@
 import dataclasses
 import datetime
 import functools
+import itertools
 import logging
 import pathlib
 import posixpath
@@ -261,7 +262,9 @@
         revisions = [
             f'{self.name}:{p.setdep_str()}' for p in self.new_packages
         ]
-        return ['--revision'] + revisions
+        return list(
+            itertools.chain.from_iterable(
+                ('--revision', r) for r in revisions))
 
     def commit_message_lines(self) -> list[str]:
         return [