Assert that bookmark icon URLs are valid before syncing

Bug: 809816

Change-Id: I4993e87ccc76ccc77e523412e82d07a662092044
Reviewed-on: https://chromium-review.googlesource.com/1058996
Commit-Queue: Alan Cutter <[email protected]>
Reviewed-by: Ben Wells <[email protected]>
Cr-Commit-Position: refs/heads/master@{#558997}
diff --git a/chrome/browser/extensions/extension_sync_data.cc b/chrome/browser/extensions/extension_sync_data.cc
index 2b24159..3d43bab2 100644
--- a/chrome/browser/extensions/extension_sync_data.cc
+++ b/chrome/browser/extensions/extension_sync_data.cc
@@ -232,6 +232,7 @@
   for (const auto& linked_icon : linked_icons_) {
     sync_pb::LinkedAppIconInfo* linked_app_icon_info =
         specifics->add_linked_app_icons();
+    DCHECK(linked_icon.url.is_valid());
     linked_app_icon_info->set_url(linked_icon.url.spec());
     linked_app_icon_info->set_size(linked_icon.size);
   }