Add enable-desktop-pwas-local-updating flag

This CL adds a feature flag in preparation for implementing local PWA
updates when changes to site manifest data are detected.

Bug: 926083
Change-Id: I8f1f79cf8492933b9b7b6b703384da3f38eaeb32
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1697662
Commit-Queue: Alan Cutter <[email protected]>
Auto-Submit: Alan Cutter <[email protected]>
Reviewed-by: Raymes Khoury <[email protected]>
Cr-Commit-Position: refs/heads/master@{#676759}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index 5f5fd3a..db6a0b3 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -577,6 +577,12 @@
     "Experimental windowing and install banner treatment for Progressive Web "
     "Apps on desktop platforms. Implies #enable-experimental-app-banners.";
 
+extern const char kDesktopPWAsLocalUpdatingName[] =
+    "Desktop PWAs local updating";
+extern const char kDesktopPWAsLocalUpdatingDescription[] =
+    "Enable installed PWAs to update their app manifest data when the site "
+    "manifest data has changed.";
+
 const char kDesktopPWAsOmniboxInstallName[] =
     "Desktop PWAs installable from the omnibox";
 const char kDesktopPWAsOmniboxInstallDescription[] =