support mutliple modifiers for key bindings

src/content/actions/setting.js

@@ -1,9 +1,23 @@
 import actions from 'content/actions';
+import * as keyUtils from 'shared/utils/keys';
 
 const set = (value) => {
+  let maps = new Map();
+  if (value.keymaps) {
+    let entries = Object.entries(value.keymaps).map((entry) => {
+      return [
+        keyUtils.fromMapKeys(entry[0]),
+        entry[1],
+      ];
+    });
+    maps = new Map(entries);
+  }
+
   return {
     type: actions.SETTING_SET,
-    value,
+    value: Object.assign({}, value, {
+      keymaps: maps,
+    })
   };
 };