Enable brotli compression for Help app and Media app.

Bug: 1034629
Change-Id: Ic7a90406c044a6fae9871cd5f1ebf1d5b79622de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1999884Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: Rachel Carpenter <carpenterr@google.com>
Cr-Commit-Position: refs/heads/master@{#731831}

chromeos/resources/BUILD.gn

@@ -69,6 +69,7 @@ grit("help_app_bundle_resources") {
   }
 
   source_is_generated = true
+  use_brotli = true
 
   outputs = [
     "grit/chromeos_help_app_bundle_resources.h",
@@ -118,6 +119,7 @@ grit("media_app_bundle_resources") {
   }
 
   source_is_generated = true
+  use_brotli = true
 
   outputs = [
     "grit/chromeos_media_app_bundle_resources.h",