Disable BrowserTest.* on Mojo FYI

Right now the BrowserTest.* tests are racy. Most of them eventually block on
loading a page.

Unforunately in --mash this is currently too slow, often going past the test
launcher's internal timeouts for output. (15s) Testing locally found they are
sometimes blocked for 25s

This leads to the entire mash_browser_tests flakily timing out, which prevents
us from bringing it back on the main waterfall.

TBR=sky@chromium.org
TEST=mash_browser_tests

Bug: 687687
Change-Id: Ib12e07e75664e8d45dc6c6745db13907c6827e23
Reviewed-on: https://chromium-review.googlesource.com/600487Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491775}

testing/buildbot/filters/mojo.fyi.browser_tests.filter

-BrowserTest.*
-
-# Failing test
--BrowserTest.FullscreenBookmarkBar
-
 # Trying to whitelist
 BrowserDialogTest.Invoke
 CastSessionBrowserTest.CreateAndDestroy