Revert of Add remoting and PPAPI tests to GN build

Revert of Add remoting and PPAPI tests to GN build (patchset #7 id:120001 of https://codereview.chromium.org/965633002/)

Reason for revert:
http://build.chromium.org/p/chromium.mac/buildstatus?builder=Mac%20GN&number=4498

ERROR at //remoting/host/BUILD.gn:56:7: Item not found
      "linux/x_server_clipboard.cc",
      ^----------------------------
You were trying to remove "linux/x_server_clipboard.cc"

Original issue's description:
> Add remoting and PPAPI tests to GN build
>
> BUG=
>
> Committed: https://crrev.com/d0437210926b14b1b7e06b2b56174fc92ade9c37
> Cr-Commit-Position: refs/heads/master@{#318539}

TBR=kelvinp@chromium.org,dpranke@chromium.org,brettw@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://crrev.com/d593eac9968cee2b5412ba22638ed16f0884c408
Cr-Commit-Position: refs/heads/master@{#318545}

[eroman, 2015-02-27 23:38:56]

Created Revert of Add remoting and PPAPI tests to GN build

[commit-bot: I haz the power, 2015-02-27 23:40:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/970443002/1

[commit-bot: I haz the power, 2015-02-27 23:41:36]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-27 23:42:12]

Patchset 1 (id:??) landed as
https://crrev.com/d593eac9968cee2b5412ba22638ed16f0884c408
Cr-Commit-Position: refs/heads/master@{#318545}