[Telemetry] Add tab API function GetJavascriptStats().

[Telemetry] Add tab property "dom_stats".

Currently, the associated function reaches into the inspector_backend, which in
turn now has a new module to communicate with the remote inspector's
"Memory" domain.  This allows us to query the remote inspector for the
DOM node count, document count, and event listener count, for a tab.

Making this change is a prerequisite to converting the Chrome Endure
endurance tests over to Telemetry from their current pyauto-based
implementation.

BUG=chromium-os:39589
TEST=tools/telemetry/run_tests InspectorMemoryTest

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=188092

[dennis_jeffrey, 2013-03-12 21:34:37]

Dave, Nat,

Please take a look.  This is a revised version of my earlier CL
(https://chromiumcodereview.appspot.com/12220086/) to add support for getting
Javascript stats from a tab.  I created a new CL since there was a major
Telemetry refactoring since my last CL.

This accounts for our discussion about adding a new tab API called
GetJavascriptStats().  This API is meant to be general enough to return any
arbitrary set of JS stats in a dictionary.  However, the current implementation
just reaches into chrome's remote inspector and gets the counts via that
protocol's Memory.getDOMCounters command.  The API function could be revised in
the future to work with different backends that may be added.

[nduca, 2013-03-13 03:58:44]

lgtm with nits. awesome.

https://codereview.chromium.org/12800004/diff/1/tools/telemetry/telemetry/cor...
File tools/telemetry/telemetry/core/tab.py (right):

https://codereview.chromium.org/12800004/diff/1/tools/telemetry/telemetry/cor...
tools/telemetry/telemetry/core/tab.py:74: def GetJavascriptStats(self,
timeout=DEFAULT_TAB_TIMEOUT):
GetDOMStats?

Sorry if you suggested that in the past and I hated it! :$ I'm fine with your
discretion at this point, this looks really good

https://codereview.chromium.org/12800004/diff/1/tools/telemetry/telemetry/cor...
tools/telemetry/telemetry/core/tab.py:84: dom_counters =
self._inspector_backend.GetDomCounters(timeout)
DOM or Dom? Just curious tbh.

Shoudl the name match the backend name? E.g. GetDomStats? That it turns into an
inspector-level GetDomCounters can just be sealed inside the backend.

https://codereview.chromium.org/12800004/diff/1/tools/telemetry/telemetry/cor...
tools/telemetry/telemetry/core/tab.py:86: 'document_count':
dom_counters['documents'],
Should this conversion to the expected return type done inside the inspector
backend? Then this is just return the backend properties and maybe an assertion
that the expected values [and only the expected values] are in the return value.

https://codereview.chromium.org/12800004/diff/1/tools/telemetry/unittest_data...
File tools/telemetry/unittest_data/dom_counter_sample.html (right):

https://codereview.chromium.org/12800004/diff/1/tools/telemetry/unittest_data...
tools/telemetry/unittest_data/dom_counter_sample.html:2: <title>DOM counter unit
test page</title>
Should we put the expectation in the description below? E..g tests expect this
page to have n elements and blah blah listeners or whatever?

[dennis_jeffrey, 2013-03-13 21:42:46]

Thanks!  Anything else before I commit?

https://codereview.chromium.org/12800004/diff/1/tools/telemetry/telemetry/cor...
File tools/telemetry/telemetry/core/tab.py (right):

https://codereview.chromium.org/12800004/diff/1/tools/telemetry/telemetry/cor...
tools/telemetry/telemetry/core/tab.py:74: def GetJavascriptStats(self,
timeout=DEFAULT_TAB_TIMEOUT):
On 2013/03/13 03:58:44, nduca wrote:
> GetDOMStats?
> 
> Sorry if you suggested that in the past and I hated it! :$ I'm fine with your
> discretion at this point, this looks really good

Yes, GetDOMStats sounds good to me.  I made that change.

https://codereview.chromium.org/12800004/diff/1/tools/telemetry/telemetry/cor...
tools/telemetry/telemetry/core/tab.py:84: dom_counters =
self._inspector_backend.GetDomCounters(timeout)
On 2013/03/13 03:58:44, nduca wrote:
> DOM or Dom? Just curious tbh.

Actually I prefer DOM when typing in MixedCase, so made that change.

I knew somebody who always wanted acronyms in MixedCaseFunctionNames to have
only the very first letter capitalized, so sometimes I do that without thinking.
 However, I couldn't find a chromium Python style rule talking about this
particular point, so I think it's just best to be consistent.

> 
> Shoudl the name match the backend name? E.g. GetDomStats? That it turns into
an
> inspector-level GetDomCounters can just be sealed inside the backend.

Done.

https://codereview.chromium.org/12800004/diff/1/tools/telemetry/telemetry/cor...
tools/telemetry/telemetry/core/tab.py:86: 'document_count':
dom_counters['documents'],
On 2013/03/13 03:58:44, nduca wrote:
> Should this conversion to the expected return type done inside the inspector
> backend? Then this is just return the backend properties and maybe an
assertion
> that the expected values [and only the expected values] are in the return
value.

Done.

https://codereview.chromium.org/12800004/diff/1/tools/telemetry/unittest_data...
File tools/telemetry/unittest_data/dom_counter_sample.html (right):

https://codereview.chromium.org/12800004/diff/1/tools/telemetry/unittest_data...
tools/telemetry/unittest_data/dom_counter_sample.html:2: <title>DOM counter unit
test page</title>
On 2013/03/13 03:58:44, nduca wrote:
> Should we put the expectation in the description below? E..g tests expect this
> page to have n elements and blah blah listeners or whatever?

Good idea - done.

[nduca, 2013-03-13 22:46:51]

ship it. lgtm.

[dtu, 2013-03-13 22:48:14]

The other stats that tonyg added had the naming @property xyz_stats() instead of
GetXyzStats().
https://chromiumcodereview.appspot.com/11576050/

[dennis_jeffrey, 2013-03-13 23:13:08]

On 2013/03/13 22:48:14, Dave Tu wrote:
> The other stats that tonyg added had the naming @property xyz_stats() instead
of
> GetXyzStats().
> https://chromiumcodereview.appspot.com/11576050/

Is this something you'd like to keep consistent across all of Telemetry?  If so,
I can make that change.

[dtu, 2013-03-13 23:26:40]

On 2013/03/13 23:13:08, dennis_jeffrey wrote:
> On 2013/03/13 22:48:14, Dave Tu wrote:
> > The other stats that tonyg added had the naming @property xyz_stats()
instead
> of
> > GetXyzStats().
> > https://chromiumcodereview.appspot.com/11576050/
> 
> Is this something you'd like to keep consistent across all of Telemetry?  If
so,
> I can make that change.

Yes, please :)

[dennis_jeffrey, 2013-03-13 23:41:10]

Done.  PTAL.

[dtu, 2013-03-13 23:46:08]

thanks! lglgtmtm

[commit-bot: I haz the power, 2013-03-13 23:52:11]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dennisjeffrey@chromium.org/12800004/6006

[commit-bot: I haz the power, 2013-03-14 16:09:16]

Change committed as 188092