ELECTRON-656 (Localize context menu labels) (#472)

- Localize context menu labels
- Update condition to setLocale for pop-out window

locale/ja-JP.json

@@ -17,6 +17,21 @@
   "Bring to Front on Notifications": "通知時に前面に表示",
   "Certificate Error": "証明書のエラー",
   "Close": "閉じる",
+  "ContextMenu": {
+    "Add to Dictionary": "辞書に追加",
+    "Copy": "コピー",
+    "Copy Email Address": "メールアドレスをコピーする",
+    "Copy Image": "イメージをコピーする",
+    "Copy Image URL": "コピー画像のURL",
+    "Copy Link": "リンクをコピーする",
+    "Cut": "カット",
+    "Inspect Element": "要素の検査",
+    "Look Up ": "見上げる",
+    "Open Link": "リンクを開く",
+    "Paste": "ペースト",
+    "Reload": "リロード",
+    "Search with Google": "Googleで検索"
+  },
   "Copy": "コピー",
   "Custom": "カスタム",
   "Cut": "切り取り",