Make mojo_benchmark understand the output it is producing.

Make mojo_benchmark understand the output it is producing.

This patch:
 - refactors the logic in mojo_benchmark so that obtaining the output
   produced by `benchmark.mojo` is separated from its analysis and
   presentation
 - makes `mojo_benchmark` parse the measurements results, as opposed to
   just streaming the output produced by `benchmark.mojo`.

This is a prerequisite for producing the chart data to be uploaded to
the performance dashboard, see domokit/mojo#474. As a bonus, we now
notice when measurement result is missing and return non-zero exit code.

R=viettrungluu@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/0acce94790935a282c3461c3fca2787e61bd2233

[ppi, 2015-10-14 23:41:13]

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

[ppi, 2015-10-14 23:42:56]

Hi Trung or Ben,

ptal.

[viettrungluu, 2015-10-15 00:45:03]

https://codereview.chromium.org/1392173006/diff/1/mojo/devtools/common/mojo_b...
File mojo/devtools/common/mojo_benchmark (right):

https://codereview.chromium.org/1392173006/diff/1/mojo/devtools/common/mojo_b...
mojo/devtools/common/mojo_benchmark:219: succeeded = False
This is a confusing pattern, since without reading it carefully it looks like
the |if not succeeded:| below could be |else:|.

You should use a different variable.

[ppi, 2015-10-15 01:15:15]

https://codereview.chromium.org/1392173006/diff/1/mojo/devtools/common/mojo_b...
File mojo/devtools/common/mojo_benchmark (right):

https://codereview.chromium.org/1392173006/diff/1/mojo/devtools/common/mojo_b...
mojo/devtools/common/mojo_benchmark:219: succeeded = False
On 2015/10/15 00:45:03, viettrungluu wrote:
> This is a confusing pattern, since without reading it carefully it looks like
> the |if not succeeded:| below could be |else:|.
> 
> You should use a different variable.

Done.

[viettrungluu, 2015-10-15 01:55:03]

lgtm

[ppi, 2015-10-15 02:04:05]

Committed patchset #2 (id:20001) manually as
0acce94790935a282c3461c3fca2787e61bd2233 (presubmit successful).