Refine UMA quality for warm-start app list cases

Refine UMA quality for warm-start app list cases

Currently "warm start" app list cases (i.e. shown via the process
singleton) have noisy UMA data. Whether the profile to show is loaded or
not has a big impact on the metric. We are only interested in the case 
that the app list view is "warm", and can be immediately shown. 
Recording cases that first must load a profile from disk, or switch the 
app list view to a different profile, count as noise and skew the 
metric. 

This change filters out the noise, fixing an incorrect assumption in 
r270615 which resulted in only the noise being recorded (and a failed 
DCHECK otherwise). Before r270615, the UMA included cases requiring a 
profile load as well as those that didn't. After r270615, only cases 
that required a profile load were being recorded. 

Note that ShowAppListInteractiveTest.ShowAppListFlag was updated in
r281213 to include both cold and warm codepaths via
StartupBrowserCreator, to cover the aforementioned DCHECK.

BUG=382793
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=282245

[Matt Giuca, 2014-07-04 04:44:41]

LGTM! Nice.

Again, please update the CL description (removing the [2/2]).

Also, the last paragraph of the CL description mentions changes to
ShowAppListInteractiveTest.ShowAppListFlag which aren't in this (or the
previous) CL. Mysterious! Can you delete this paragraph or did you mean to
update those tests?

[Matt Giuca, 2014-07-08 00:30:53]

"not has a big impact on the metric" (from the CL description)?

[tapted, 2014-07-08 00:40:44]

On 2014/07/08 00:30:53, Matt Giuca wrote:
> "not has a big impact on the metric" (from the CL description)?

whoops hotkey fail. Although I wish rietveld had a description history so I
didn't have to search my mail :/

[tapted, 2014-07-10 00:10:15]

The CQ bit was checked by tapted@chromium.org

[commit-bot: I haz the power, 2014-07-10 00:12:54]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tapted@chromium.org/366233002/20001

[commit-bot: I haz the power, 2014-07-10 03:55:10]

Change committed as 282245