[System PWAs] Add about:flags entry.

This CL adds an about:flags entry for the SystemWebApps feature.

Bug: 836128
Change-Id: I83ae0dcd55885ca5e95fe10fb6384aa844ae25df
Reviewed-on: https://chromium-review.googlesource.com/1240055
Reviewed-by: Alan Cutter <[email protected]>
Commit-Queue: calamity <[email protected]>
Cr-Commit-Position: refs/heads/master@{#594181}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 79127348..cc2151f 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -2330,6 +2330,9 @@
      flag_descriptions::kEnableDesktopPWAsLinkCapturingName,
      flag_descriptions::kEnableDesktopPWAsLinkCapturingDescription, kOsDesktop,
      FEATURE_VALUE_TYPE(features::kDesktopPWAsLinkCapturing)},
+    {"enable-system-webapps", flag_descriptions::kEnableSystemWebAppsName,
+     flag_descriptions::kEnableSystemWebAppsDescription, kOsDesktop,
+     FEATURE_VALUE_TYPE(features::kSystemWebApps)},
     {"use-sync-sandbox", flag_descriptions::kSyncSandboxName,
      flag_descriptions::kSyncSandboxDescription, kOsAll,
      SINGLE_VALUE_TYPE_AND_VALUE(