Move some generic functions to app_platform_metrics_utils.

Move some generic functions to app_platform_metrics_utils.*, to prepare
for adding app platform input metrics, because those functions will be
used for app platform input metrics.

This is a pure refactor, no function change.

BUG=1261675

Change-Id: Ib0b73830452cb2d04e6e4c8239c5e3d5d21544c9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3233581
Reviewed-by: Dominick Ng <[email protected]>
Commit-Queue: Nancy Wang <[email protected]>
Cr-Commit-Position: refs/heads/main@{#933338}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 7935866..5a7ee31 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -4536,6 +4536,8 @@
       "apps/app_service/metrics/app_platform_metrics.h",
       "apps/app_service/metrics/app_platform_metrics_service.cc",
       "apps/app_service/metrics/app_platform_metrics_service.h",
+      "apps/app_service/metrics/app_platform_metrics_utils.cc",
+      "apps/app_service/metrics/app_platform_metrics_utils.h",
       "apps/app_service/publishers/arc_apps.cc",
       "apps/app_service/publishers/arc_apps.h",
       "apps/app_service/publishers/arc_apps_factory.cc",