Keyboard Shortkey for ctrl+insert is not working.

Earlier only ctrl+C is handled, I have added key for Ctrl+Insert also
So if their is any selection then it will get copied like that happen
in case of Ctrl+C, That is selected text get copied to clipboard.

BUG=390837

Review URL: https://codereview.chromium.org/629823002

git-svn-id: svn://svn.chromium.org/blink/trunk@183575 bbb929c8-8fbe-4397-9dbb-9b2b20218538