[Telemetry] Add indentation to json_output & chart_json_output.

[Telemetry] Add indentation to json_output & chart_json_output.

Rationale: ocassionally I find it useful to look at json_output to debug.
Indenting the file make it a lot more readable. The downside is this increases
the file size, but it shouldn't matter for small files like these.

An example Results.json with ~2000 values tested on local machine:
Without indent: 472K
With indentation: 692K

Committed: https://crrev.com/cc27e302c16fcf0d0108e077567cd2d748d6740d
Cr-Commit-Position: refs/heads/master@{#317175}

[nednguyen, 2015-02-19 22:44:21]

nednguyen@google.com changed reviewers:
+ eakuefner@chromium.org, sullivan@chromium.org

[sullivan, 2015-02-19 22:45:12]

lgtm

[eakuefner, 2015-02-19 22:48:11]

My approach for when I need to read JSON output from Telemetry has usually been
to just pipe it through 'python -m json.tool'. json.tool is the json module's
built-in pretty printer. Take a look and see if this suits your needs.

[eakuefner, 2015-02-19 22:49:05]

On 2015/02/19 at 22:48:11, eakuefner wrote:
> My approach for when I need to read JSON output from Telemetry has usually
been to just pipe it through 'python -m json.tool'. json.tool is the json
module's built-in pretty printer. Take a look and see if this suits your needs.

So to be clear, this is not lgtm unless json.tool isn't suitable for some
reason.

[eakuefner, 2015-02-19 22:53:19]

On 2015/02/19 at 22:49:05, eakuefner wrote:
> On 2015/02/19 at 22:48:11, eakuefner wrote:
> > My approach for when I need to read JSON output from Telemetry has usually
been to just pipe it through 'python -m json.tool'. json.tool is the json
module's built-in pretty printer. Take a look and see if this suits your needs.
> 
> So to be clear, this is not lgtm unless json.tool isn't suitable for some
reason.

Discussed offline with Ned about usability benefits + relative overhead; lgtm.

[nednguyen, 2015-02-19 22:54:00]

The CQ bit was checked by nednguyen@google.com

[nednguyen, 2015-02-19 22:54:23]

On 2015/02/19 22:53:19, eakuefner wrote:
> On 2015/02/19 at 22:49:05, eakuefner wrote:
> > On 2015/02/19 at 22:48:11, eakuefner wrote:
> > > My approach for when I need to read JSON output from Telemetry has usually
> been to just pipe it through 'python -m json.tool'. json.tool is the json
> module's built-in pretty printer. Take a look and see if this suits your
needs.
> > 
> > So to be clear, this is not lgtm unless json.tool isn't suitable for some
> reason.
> 
> Discussed offline with Ned about usability benefits + relative overhead; lgtm.

Yeah, we already save the trace files whose size 100x of these files.

[commit-bot: I haz the power, 2015-02-19 22:54:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/940123003/1

[commit-bot: I haz the power, 2015-02-19 23:51:23]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-19 23:52:12]

Patchset 1 (id:??) landed as
https://crrev.com/cc27e302c16fcf0d0108e077567cd2d748d6740d
Cr-Commit-Position: refs/heads/master@{#317175}