[mac] Init spellcheck service.

BUG=454992

Review URL: https://codereview.chromium.org/928473002

Cr-Commit-Position: refs/heads/master@{#317179}

chrome/browser/spellchecker/spellcheck_message_filter_mac.cc

@@ -265,6 +265,13 @@ void SpellCheckMessageFilterMac::OnRequestTextCheck(
     std::vector<SpellCheckMarker> markers) {
   DCHECK(!text.empty());
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+
+  // Initialize the spellcheck service if needed. The service will send the
+  // language code for text breaking to the renderer. (Text breaking is required
+  // for the context menu to show spelling suggestions.) Initialization must
+  // happen on UI thread.
+  SpellcheckServiceFactory::GetForRenderProcessId(render_process_id_);
+
   // Erase invalid markers (with offsets out of boundaries of text length).
   markers.erase(
       std::remove_if(