Make Ctrl + T from apps focus the new tab's omnibox on Linux and ChromeOS.
This CL fixes an issue where pressing Ctrl + T from a non-tabbed browser
would not focus the omnibox if the WebView of the new tab's browser window
was not focused.
This has been fixed by refocusing the omnibox after the browser Show() on
ChromeOS and by re-adding an ifdef that was introduced to Linux as part
of a ChromeOS specific fix in r173840.
BUG=399133
Review URL: https://codereview.chromium.org/
1091953004
Cr-Commit-Position: refs/heads/master@{#327660}