[Temp] Replace #ifdef(OS_LINUX) with #ifdef(USE_X11) for x11 specific code

This fixes the Ozone FYI builder.

https://codereview.chromium.org/213283004 added X11 specific code but uses OS_LINUX to enable it. The Ozone build is a linux build but without X11, thus failing tests.

TESTS=Manually ran content_browsertests content_unittests components_unittests with an Ozone build

Review URL: https://codereview.chromium.org/217323008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@261058 0039d316-1c4b-4281-b951-d872f2087c98
[Temp] We use TextEditKeyBindingsDelegate and TextEditCommand for x11. These classes don't have any x11 specific dependencies. This CL adds support to use them for all platforms on Linux.

This fixes linking error when building Chromium with Ozone.

Review URL: https://codereview.chromium.org/225583005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@262370 0039d316-1c4b-4281-b951-d872f2087c98