Add perf_expectations/ and empty expectations JSON.
Add perf_expectations/ and empty expectations JSON.

Adding the directory and empty file now so I can
continue making perf-related changes to the buildbot
infrastructure.  The expectations file will get filled
in with some initial values after the infrastructure
changes have been made.

BUG=18579
TEST=none

Review URL: http://codereview.chromium.org/178024

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@24817 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser