Teach mojo_benchmark to control caching conditions.

Teach mojo_benchmark to control caching conditions.

This patch makes mojo_benchmark run each benchmark twice, first with a
flushed cache and again without clearing the cache, yielding cold start
and warm start results.

This currently supports only flushing the url_response_disk_cache, we
will want to clear the network service cache too.

R=qsr@google.com

Committed: https://chromium.googlesource.com/external/mojo/+/152015f44e134512ba45524e562c7c547b28886d

[ppi, 2015-09-07 11:00:48]

ppi@chromium.org changed reviewers:
+ qsr@chromium.org

[ppi, 2015-09-07 11:00:48]

Hi Ben,

ptal.

[qsr (NOT THE RIGHT qsr), 2015-09-07 11:29:57]

qsr@google.com changed reviewers:
+ qsr@google.com

[qsr (NOT THE RIGHT qsr), 2015-09-07 11:29:58]

https://codereview.chromium.org/1320403003/diff/1/mojo/devtools/common/mojo_b...
File mojo/devtools/common/mojo_benchmark (right):

https://codereview.chromium.org/1320403003/diff/1/mojo/devtools/common/mojo_b...
mojo/devtools/common/mojo_benchmark:47: _CACHE_SERVICE_URL =
'https://core.mojoapps.io/url_response_disk_cache.mojo'
Why both URLs?

[ppi, 2015-09-07 11:32:58]

https://codereview.chromium.org/1320403003/diff/1/mojo/devtools/common/mojo_b...
File mojo/devtools/common/mojo_benchmark (right):

https://codereview.chromium.org/1320403003/diff/1/mojo/devtools/common/mojo_b...
mojo/devtools/common/mojo_benchmark:47: _CACHE_SERVICE_URL =
'https://core.mojoapps.io/url_response_disk_cache.mojo'
On 2015/09/07 11:29:58, qsr (NOT THE RIGHT qsr) wrote:
> Why both URLs?

So that this doesn't break when we switch the callers over to new urls. We can
skip this speculative precaution if you'd prefer that.

[qsr (NOT THE RIGHT qsr), 2015-09-07 11:40:28]

On 2015/09/07 11:32:58, ppi wrote:
>
https://codereview.chromium.org/1320403003/diff/1/mojo/devtools/common/mojo_b...
> File mojo/devtools/common/mojo_benchmark (right):
> 
>
https://codereview.chromium.org/1320403003/diff/1/mojo/devtools/common/mojo_b...
> mojo/devtools/common/mojo_benchmark:47: _CACHE_SERVICE_URL =
> 'https://core.mojoapps.io/url_response_disk_cache.mojo'
> On 2015/09/07 11:29:58, qsr (NOT THE RIGHT qsr) wrote:
> > Why both URLs?
> 
> So that this doesn't break when we switch the callers over to new urls. We can
> skip this speculative precaution if you'd prefer that.

We would need to change half the world when we do this. I'd rather have the
change be a change of URL, then removing some code...

[ppi, 2015-09-07 11:48:00]

Makes sense, done, ptal.

[qsr (NOT THE RIGHT qsr), 2015-09-07 12:01:10]

lgtm

[ppi, 2015-09-07 12:05:48]

Committed patchset #2 (id:20001) manually as
152015f44e134512ba45524e562c7c547b28886d (presubmit successful).