Implement a better dashboard for running benchmarks

Implement a better dashboard for running benchmarks

- Provide a 'Run' button instead of running on page reload
- Display median samples from saved report as a baseline for comparison.
- Provide a menu for choosing the saved report.
- Display the median, max, and number of samples gathered.

Also:
- Simplified the JSON benchmark a bit.
- Increase the default number of samples and decrease their duration.
- Collect one sample from each benchmark in each loop (round-robin).

This was to try to reduce the amount of varation between runs.
It seems to have helped somewhat, but benchmark results can still
vary by up to about 20% when opening a new tab.

BUG=
R=sgjesse@google.com

Committed: https://github.com/dart-lang/dart-protoc-plugin/commit/3c227864999d1a9700c8623fb7d5f28dad782387

[skybrian, 2015-09-05 06:54:56]

skybrian@google.com changed reviewers:
+ sgjesse@google.com

[Søren Gjesse, 2015-09-08 06:43:54]

lgtm

Maybe look at how the Octane benchmark (https://github.com/chromium/octane) run
benchmarks. It seems to have pretty low variation on the scores.

https://chromiumcodereview.appspot.com/1330723003/diff/1/benchmark/lib/dashbo...
File benchmark/lib/dashboard_view.dart (right):

https://chromiumcodereview.appspot.com/1330723003/diff/1/benchmark/lib/dashbo...
benchmark/lib/dashboard_view.dart:5: library protoc.benchmark.html_view;
Might have been easier to put more of this into the HTML file and lookup more
elements by name instead of building the whole DOM in code. I guess you have a
good reason for doing it this way.

[skybrian, 2015-09-08 17:10:37]

Committed patchset #1 (id:1) manually as
3c227864999d1a9700c8623fb7d5f28dad782387 (presubmit successful).

[skybrian, 2015-09-08 17:25:11]

I ran Octane twice in two tabs. The overall average was very close (22008 versus
22370) but the Typescript benchmark's variation was similar to what I'm seeing
(26022 versus 23793). 

So I think it depends on the benchmark, and some of Octane's benchmarks are very
stable so the average is good.

They recommend restarting the browser each time you run the benchmark.

https://chromiumcodereview.appspot.com/1330723003/diff/1/benchmark/lib/dashbo...
File benchmark/lib/dashboard_view.dart (right):

https://chromiumcodereview.appspot.com/1330723003/diff/1/benchmark/lib/dashbo...
benchmark/lib/dashboard_view.dart:5: library protoc.benchmark.html_view;
On 2015/09/08 06:43:54, Søren Gjesse wrote:
> Might have been easier to put more of this into the HTML file and lookup more
> elements by name instead of building the whole DOM in code. I guess you have a
> good reason for doing it this way.

It's because I wanted to keep each view self-contained and all in one place.

The template isn't very readable though. Perhaps setting innerHtml to a
triple-quoted string and querying it for sub-elements would work better.