Update report generation to check for a 'perf_measurements' file.

The latest version of telemetry_Crosperf generates a perf_measurements
file, containing the test results, rather than a keyval file.  This CL
checks for perf_measurements, and reads it, if it is there.  This
change is backwards compatible with the older versions of telemetry_Crosperf
that used the keyval file.

BUG=None
TEST=Tested this with the results only in a keyval file and only in a
perf_measurements file.  Got acceptable test reports either way.

Change-Id: If10a62b2f7fbe89d35c1ebe789a81764c9d134e4
Reviewed-on: https://chrome-internal-review.googlesource.com/148295
Reviewed-by: Luis Lozano <llozano@chromium.org>
Commit-Queue: Caroline Tice <cmtice@google.com>
Tested-by: Caroline Tice <cmtice@google.com>
3 files changed