[indicators] Battery icon turns red at 30%

I'd just follow what we have with some other phones, and showing low battery only when < 15%

@rsalveti - According to the current indicators specs, the charge level should be visually supported through the different states of the battery indicator icon (i.e. 20%, 40%, 60%, 80%,100% & battery charged) in the status bar (https://drive.google.com/a/canonical.com/#folders/0BzbnWoHmYF3ablBITVByRnpzdEk)

In this case, when the phone drops below 20% power, the battery indicator should turn red giving a nudge to recharge.

@charles can you check, seems its not doing it per spec or maybe theme is wrong

So, what the spec says is:

> * The charge level should be visually supported through the different states of the battery indicator icon (i.e. 20%, 40%, 60%, 80%,100% & battery charged) in the status bar.
> * When the phone drops below 20% power, the battery indicator should turn red giving a nudge to recharge.

I-power currently picks the closest match of the -000, -020, -040, -060, -080, and -100 icons; e.g. a charge of 51% will get the -060 icon, and a charge of 49% will get the -040 icon. This is /usually/ The Right Thing because it minimizes the difference between the icon level and the actual battery level.

However this does mean 29% shows red. So we need a special case to treat the 20-30% range as a special case that deviates from the "closest match" approach, such as:

[0%..10%) battery-000
[10%..20%) battery-020
[20%...50%) battery-040
[50%..70%) battery-060
[70%..90%) battery-080
[90%..100%] battery-100

This works but isn't a great fix because the icon-to-label shear can be up to 20%: if the battery is at 20%, the label will read 20% and the icon will show 40%.

We also can't just change the 20% icon to black because we also want to maintain compatibility with other in-house and third-party icon themes on Desktop.

IMO we should do the closest match / special case approach listed above but ALSO add new charging/discharging icons for battery-010, -030, -050, -070, and -090. i-power would generally match to the nearest 10% icon, add a special case for [20-25%], and use the existing GNOME icon names as fallbacks.fallbacks.

This approach would:

(a) Fix this bug

(b) Not regress on icon-to-label shear. (Currently the max is 10%, under this scheme the worst case would be a battery at 20% and an icon at -030) and in the general case it would /reduce/ the shear since we'd be matching to the closest 10% instead of closest 20%.

(c) Maintain compatibility with other desktop icon themes by using the current names as fallbacks

To be a little more precise about the previous comment, I suggest:

1. that ubuntu-themes add new icons:

* ubuntu-mobile/status/scalable/battery-010.svg
* ubuntu-mobile/status/scalable/battery-010-charging.svg
* ubuntu-mobile/status/scalable/battery-030.svg
* ubuntu-mobile/status/scalable/battery-030-charging.svg
* ubuntu-mobile/status/scalable/battery-050.svg
* ubuntu-mobile/status/scalable/battery-050-charging.svg
* ubuntu-mobile/status/scalable/battery-070.svg
* ubuntu-mobile/status/scalable/battery-070-charging.svg
* ubuntu-mobile/status/scalable/battery-090.svg
* ubuntu-mobile/status/scalable/battery-090-charging.svg

2. that indicator-power try to match to the closest 10% =except= for [20-25%] which would be special cased to -030 to avoid the red 20% icon:

[0%..5%) battery-000
[5%..15%) battery-010
[15%..19%) battery-020
[20%..35%) battery-030
[35%..45%) battery-040
[45%..55%) battery-050
[55%..65%) battery-060
[65%..75%) battery-070
[75%..85%) battery-080
[85%..95%) battery-090
[95%..100%] battery-100

3. that indicator-power keep providing the current icon names as fallbacks so that this fix doesn't break compatibility with other icon themes

According to Paty in IRC, this is fine with Design and tiheum's going to add the new needed icons.

Also, please keep e.g. laptop use in mind when designing this. I'm currently on a laptop, and the battery indicator shows a red-with-a-little-left icon, when I have 1h10min of battery left (which feels a bit ridiculous). The percentage is at 22%.
See also the previous bug #743823, which apparently has regressed since 2011?

This bug was fixed in the package indicator-power - 12.10.6+15.04.20150212-0ubuntu1

---------------
indicator-power (12.10.6+15.04.20150212-0ubuntu1) vivid; urgency=medium

  [ Charles Kerr ]
  * Use the new power level icons for a more accurate display of the
    battery level. (LP: #1388235)
 -- CI Train Bot <email address hidden> Thu, 12 Feb 2015 22:45:30 +0000

This bug was fixed in the package ubuntu-themes - 14.04+15.04.20150212-0ubuntu1

---------------
ubuntu-themes (14.04+15.04.20150212-0ubuntu1) vivid; urgency=medium

  [ Matthieu James ]
  * Added battery icons for more charge levels: 10%, 30%, 50%, 70% and
    90%. (LP: #1388235)
 -- CI Train Bot <email address hidden> Thu, 12 Feb 2015 22:46:11 +0000

This bug was fixed in the package ubuntu-themes - 14.04+15.04.20150217~rtm-0ubuntu1

---------------
ubuntu-themes (14.04+15.04.20150217~rtm-0ubuntu1) 14.09; urgency=medium

  [ Charles Kerr ]
  * Add new power icons for bug #1388235 (LP: #1388235)
 -- CI Train Bot <email address hidden> Tue, 17 Feb 2015 16:43:29 +0000

See also bug #1559731