remoting/host: Fix the cros chrome-sdk build.

Guard the x11 source_set behind the use_x11 option.

R=yuweih@chromium.org

Bug: 867013
Test: none
Change-Id: I378652631f42609843b5a7f32d26bacccd63b5a6
Reviewed-on: https://chromium-review.googlesource.com/1150637
Reviewed-by: Yuwei Huang <yuweih@chromium.org>
Commit-Queue: James Hawkins <jhawkins@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578054}
1 file changed