toolchain-utils: Add loading.desktop@@typical to nightly tests.

page_cycler_v2.typical_25 is deprecated (and flaky!).  The
recommended replacement is loading.desktop@@typical.  This CL updates
our nightly performance test infrastructure to handle
loading.desktop@@typical.

BUG=chromium:916340
TEST=Tested with nightly run on chrotomation2.

Change-Id: I6366b3a8e6a2926ad759a209cfded890e3109810
Reviewed-on: https://chromium-review.googlesource.com/1382826
Commit-Ready: Caroline Tice <cmtice@chromium.org>
Tested-by: Caroline Tice <cmtice@chromium.org>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
4 files changed