Add spellcheck smoke test

Exposes the spellcheck provider as window.spellChecker, which allows it to be
called from tests.

preload.js

@@ -46,17 +46,7 @@
   }
   resetSelection();
 
-  // Reset the selection when clicking around, before the spell-checker runs and the context menu shows.
-  window.addEventListener('mousedown', resetSelection);
-
-  // The spell-checker runs when the user clicks on text and before the 'contextmenu' event fires.
-  // Thus, we may retrieve spell-checking suggestions to put in the menu just before it shows.
-  webFrame.setSpellCheckProvider(
-    'en-US',
-    // Not sure what this parameter (`autoCorrectWord`) does: https://github.com/atom/electron/issues/4371
-    // The documentation for `webFrame.setSpellCheckProvider` passes `true` so we do too.
-    true,
-    new SpellCheckProvider('en-US').on('misspelling', function(suggestions) {
+  window.spellChecker = new SpellCheckProvider(window.config.locale).on('misspelling', function(suggestions) {
       // Prime the context menu with spelling suggestions _if_ the user has selected text. Electron
       // may sometimes re-run the spell-check provider for an outdated selection e.g. if the user
       // right-clicks some misspelled text and then an image.
@@ -65,7 +55,21 @@
         // Take the first three suggestions if any.
         selection.spellingSuggestions = suggestions.slice(0, 3);
       }
-    }));
+  });
+
+  // Reset the selection when clicking around, before the spell-checker runs and the context menu shows.
+  window.addEventListener('mousedown', resetSelection);
+
+  // The spell-checker runs when the user clicks on text and before the 'contextmenu' event fires.
+  // Thus, we may retrieve spell-checking suggestions to put in the menu just before it shows.
+
+  webFrame.setSpellCheckProvider(
+    'en-US',
+    // Not sure what this parameter (`autoCorrectWord`) does: https://github.com/atom/electron/issues/4371
+    // The documentation for `webFrame.setSpellCheckProvider` passes `true` so we do too.
+    true,
+    spellChecker
+  );
 
   window.addEventListener('contextmenu', function(e) {
     // Only show the context menu in text editors.

test/index.html

@@ -654,6 +654,7 @@
   <script type="text/javascript" src="reliable_trigger_test.js"></script>
   <script type="text/javascript" src="backup_test.js"></script>
   <script type="text/javascript" src="i18n_test.js"></script>
+  <script type="text/javascript" src="spellcheck_test.js"></script>
 
   <script type="text/javascript" src="fixtures.js"></script>
   <script type="text/javascript" src="fixtures_test.js"></script>

test/spellcheck_test.js

@@ -0,0 +1,10 @@
+/*
+ * vim: ts=4:sw=4:expandtab
+ */
+
+describe('spellChecker', function() {
+  it('should work', function() {
+    assert(window.spellChecker.spellCheck('correct'));
+    assert(!window.spellChecker.spellCheck('fhqwgads'));
+  });
+});