Rename chromium-linux* ports to linux*

Also renames the ChromiumLinuxPort class to LinuxPort.

A later change will update the relevant LayoutTest platform directories
accordingly.

BUG=231188
R=ojan@chromium.org

Review URL: https://codereview.chromium.org/18144010

git-svn-id: svn://svn.chromium.org/blink/trunk@153306 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove concept of port-specific TestExpectations within Chromium ports

The last Chromium per-port expectations were for Android and were removed in bb1a531d443eae58e52275544ec08e03a0f3dfda

R=ojan@chromium.org

Review URL: https://codereview.chromium.org/18190002

git-svn-id: svn://svn.chromium.org/blink/trunk@153307 bbb929c8-8fbe-4397-9dbb-9b2b20218538