Revert "Add multi results in legacy perf dashboard script."

This reverts commit 3ca3fb27df6b1e3b2a7bb200e50e7361395995af.

Reason for revert:
Seems to be the incorrect way to handle multi-results. Instead of
returning an array of values, we should compute the average and return
a standard deviation as the last result.

https://chromeperf.appspot.com/report?sid=3b11bf2aa2cf2281472588fed4dfc1e0a9f514ff10bd9db09cb208c5306ac3c9

Original change's description:
> Add multi results in legacy perf dashboard script.
> 
> Currently when the script reads multiple results it outputs the
> last value read as well as a zero placehold for standard deviation.
> 
> According to benjhayden@ we can return all results in an array.
> This change does just that and adds a test. It also updates the
> expected unit test output.
> 
> Bug: 900677
> Change-Id: Icc38808ea83caddbdf6b8582e2ddc34db4f8cdf0
> Reviewed-on: https://chromium-review.googlesource.com/c/1338468
> Reviewed-by: Ned Nguyen <nednguyen@google.com>
> Commit-Queue: Jamie Madill <jmadill@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#608882}

TBR=jmadill@chromium.org,benjhayden@chromium.org,nednguyen@google.com,eyaich@chromium.org

Change-Id: I24fe0fae6607bf4d1bf8fb55d2c4f78d18a74b71
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 900677
Reviewed-on: https://chromium-review.googlesource.com/c/1341087
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609076}
9 files changed