Check for 'significant' results at report generation instead of caching.

The current implementation of the option that masks unimportant results
discards the uninteresting results before caching the test results. After
further thought, that was not the right design choice.  Among other things it
can cause confusing results, such as seen in issue 357346.  We should always
cache all the results, and do the result filtering during report generation.
This CL makes that change.

BUG=357346,357343
TEST=Ran crosperf tests with and without cache hits, and with and without entreies in the json file.  It all seems to work as expected.

Change-Id: I778e5614c73bf751ebaa2d4606af636275247c60
Reviewed-on: https://chrome-internal-review.googlesource.com/159108
Reviewed-by: Yunlian Jiang <yunlian@google.com>
Commit-Queue: Caroline Tice <cmtice@google.com>
Tested-by: Caroline Tice <cmtice@google.com>
3 files changed