popupMenu: restore minimum slider width, override sound slider only

Thie reverts 3327cc3 and makes only a specific change to
the Applications input sliders in the sound applet. The original
change would result in regressions in spices that may unknowingly
rely on the slider width to size their popups.

data/theme/cinnamon.css

@@ -205,7 +205,7 @@ StScrollBar StButton#vhandle:hover {
 }
 .popup-slider-menu-item {
  height: 1em;
- min-width: 6em;
+ min-width: 15em;
  -slider-height: 0.3em;
  -slider-background-color: #666666;
  -slider-border-color: #555555;

files/usr/share/cinnamon/applets/power@cinnamon.org/applet.js

@@ -206,7 +206,6 @@ class BrightnessSlider extends PopupMenu.PopupSliderMenuItem {
  this.removeActor(this._slider);
  this.addActor(this.icon, {span: 0});
  this.addActor(this._slider, {span: -1, expand: true});
- this._slider.style = "min-width: 10em;";
 
  this.label = label;
  this.tooltipText = label;

files/usr/share/cinnamon/applets/sound@cinnamon.org/applet.js

@@ -455,6 +455,7 @@ class StreamMenuSection extends PopupMenu.PopupMenuSection {
  }
 
  let slider = new VolumeSlider(applet, stream, name, iconName);
+ slider._slider.style = "min-width: 6em;";
  this.addMenuItem(slider);
  }
 }