Update manager Google Chrome update error "Requires Installation of Untrusted Packages" on Ubuntu

I have tried to update Chrome browser. but, It keep showing this error message "Requires Installation of Untrusted Packages"

After Google, nothing really worked what they said.

I just typed apt-get command instead of using update manager.
You just need to type 'sudo apt-get upgrade google-chrome-stable' and 'Y' two times. that's it.
and restart your computer. then you can use latest Chrome version.

$ sudo apt-get upgrade google-chrome-stable
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be upgraded:
  google-chrome-stable
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 27.2 MB of archives.
After this operation, 2,556 kB of additional disk space will be used.
Do you want to continue [Y/n]? Y
WARNING: The following packages cannot be authenticated!
  google-chrome-stable
Install these packages without verification [y/N]? Y
Get:1 http://dl.google.com/linux/chrome/deb/ stable/main google-chrome-stable amd64 18.0.1025.162-r131933 [27.2 MB]
Fetched 27.2 MB in 12s (2,249 kB/s)                                            
(Reading database ... 262166 files and directories currently installed.)
Preparing to replace google-chrome-stable 17.0.963.78-r125577 (using .../google-chrome-stable_18.0.1025.162-r131933_amd64.deb) ...
Unpacking replacement google-chrome-stable ...
Processing triggers for man-db ...
Processing triggers for bamfdaemon ...
Rebuilding /usr/share/applications/bamf.index...
Processing triggers for desktop-file-utils ...
Processing triggers for gnome-menus ...
Setting up google-chrome-stable (18.0.1025.162-r131933) ...