input[type=search]: Flip the position of cancel button in RTL.

We didn't do it because Safari didn't.  Safari recently changed the behavior.
This CL removes a UA style to force LTR, and update some tests and WebUI style.

BUG=67848
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2219373002
Cr-Commit-Position: refs/heads/master@{#410495}
12 files changed