[WebAppProvider] Stop backwards compatibility syncing sorting ordinals

Stops syncing page and launch ordinals of webapps back to the shadow
extension installations.

R=loyso@chromium.org

Bug: 1099615
Change-Id: I520b1c375b07743b330e376b81705a5cfd56c8b9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2485435Reviewed-by: Finnur Thorarinsson <finnur@chromium.org>
Reviewed-by: Alexey Baskakov <loyso@chromium.org>
Commit-Queue: Daniel Murphy <dmurph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820804}

chrome/browser/extensions/chrome_app_sorting.cc

@@ -376,7 +376,7 @@ void ChromeAppSorting::SetAppLaunchOrdinal(
   if (web_app_registrar_ && web_app_registrar_->IsInstalled(extension_id)) {
     web_app_sync_bridge_->SetUserLaunchOrdinal(extension_id,
                                                new_app_launch_ordinal);
-    // Fall through on purpose to ensure Extensions system has correct data.
+    return;
   }
 
   std::unique_ptr<base::Value> new_value =
@@ -462,7 +462,7 @@ void ChromeAppSorting::SetPageOrdinal(
 
   if (web_app_registrar_ && web_app_registrar_->IsInstalled(extension_id)) {
     web_app_sync_bridge_->SetUserPageOrdinal(extension_id, new_page_ordinal);
-    // Fall through on purpose to ensure Extensions system has correct data.
+    return;
   }
 
   std::unique_ptr<base::Value> new_value =