Stop trying to fetch bookmark apps from the store

For regular apps we queue requests[1] to fetch the app from the store[2] (or
wherever the app set as its update_url) and then install that[3]. The only thing
we actually sync for them are settings[4][5]- the rest is downloaded.

For bookmark apps, we can't actually fetch them from the store so we sync all
the necessary data[6] and update the app manually[7].

Even after we manually update a Bookmark App[7] we don't return so we are trying
to fetch bookmark apps from the store. This patch immediately returns after
updating the app.

[1] https://cs.chromium.org/chromium/src/chrome/browser/extensions/extension_sync_service.cc?type=cs&sq=package:chromium&l=522
[2] https://cs.chromium.org/chromium/src/extensions/browser/updater/extension_downloader.cc?q=extension+downloader&sq=package:chromium&dr=CSs&l=525
[3] https://cs.chromium.org/chromium/src/chrome/browser/extensions/updater/extension_updater.cc?gsn=CheckForUpdatesSoon&l=433
[4] https://cs.chromium.org/chromium/src/components/sync/protocol/app_specifics.proto?dr&l=57
[5] https://cs.chromium.org/chromium/src/components/sync/protocol/extension_specifics.proto?dr&l=20
[6] https://cs.chromium.org/chromium/src/components/sync/protocol/app_specifics.proto?dr&l=82
[7] https://cs.chromium.org/chromium/src/chrome/browser/extensions/extension_sync_service.cc?type=cs&sq=package:chromium&l=511

Bug: 745097
Change-Id: Ie5b60648738e5ad14076018999c2509bbe263979
Reviewed-on: https://chromium-review.googlesource.com/571520Reviewed-by: Ben Wells <benwells@chromium.org>
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487371}

chrome/browser/extensions/extension_sync_service.cc

@@ -507,8 +507,11 @@ void ExtensionSyncService::ApplySyncData(
           profile_, id, extension_sync_data.launch_type());
     }
 
-    if (!extension_sync_data.bookmark_app_url().empty())
+    if (!extension_sync_data.bookmark_app_url().empty()) {
+      // Handles creating and updating the bookmark app.
       ApplyBookmarkAppSyncData(extension_sync_data);
+      return;
+    }
   }
 
   // Finally, trigger installation/update as required.