Fix string escaping in (un)install scripts of native messaging example

chrome/common/extensions/docs/examples/api/nativeMessaging/host/uninstall_host.sh

 #!/bin/sh
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 set -e
 
-if [ $(uname -s) == 'Darwin' ]; then
+if [ "$(uname -s)" == "Darwin" ]; then
   if [ "$(whoami)" == "root" ]; then
     TARGET_DIR="/Library/Google/Chrome/NativeMessagingHosts"
   else
-    TARGET_DIR=\
-        "$HOME/Library/Application Support/Google/Chrome/NativeMessagingHosts"
+    TARGET_DIR="$HOME/Library/Application Support/Google/Chrome/NativeMessagingHosts"
   fi
 else
   if [ "$(whoami)" == "root" ]; then
     TARGET_DIR="/etc/opt/chrome/native-messaging-hosts"
   else
-    TARGET_DIR='$HOME/.config/google-chrome/NativeMessagingHosts'
+    TARGET_DIR="$HOME/.config/google-chrome/NativeMessagingHosts"
   fi
 fi
 
 HOST_NAME=com.google.chrome.example.echo
-rm $TARGET_DIR/com.google.chrome.example.echo.json
-echo Native messaging host $HOST_NAME has been uninstalled.
+rm "$TARGET_DIR/com.google.chrome.example.echo.json"
+echo "Native messaging host $HOST_NAME has been uninstalled."