Device: Try harder to properly setup the charging LED on plug/unplug (#10855)

By debouncing the call and delaying it some more.

frontend/device/generic/device.lua

@@ -72,6 +72,7 @@ local Device = {
     isGSensorLocked = no,
     canToggleMassStorage = no,
     canToggleChargingLED = no,
+    _updateChargingLED = nil,
     canUseWAL = yes, -- requires mmap'ed I/O on the target FS
     canRestart = yes,
     canSuspend = no,
@@ -1002,6 +1003,9 @@ function Device:_UIManagerReady(uimgr)
     -- Setup PM event handlers
     -- NOTE: We keep forwarding the uimgr reference because some implementations don't actually have a module-local UIManager ref to update
     self:_setEventHandlers(uimgr)
+
+    -- Returns a self-debouncing scheduling call (~4s to give some leeway to the kernel, and debounce to deal with potential chattering)
+    self._updateChargingLED = UIManager:debounce(4, false, function() self:setupChargingLED() end)
 end
 -- In case implementations *also* need a reference to UIManager, *this* is the one to implement!
 function Device:UIManagerReady(uimgr) end
@@ -1105,15 +1109,16 @@ end
 
 -- The common operations that should be performed when the device is plugged to a power source.
 function Device:_beforeCharging()
-    -- Leave the kernel some time to figure it out ;o).
-    UIManager:scheduleIn(1, function() self:setupChargingLED() end)
+    -- Invalidate the capacity cache to make sure we poll up-to-date values for the LED check
+    self.powerd:invalidateCapacityCache()
+    self:_updateChargingLED()
     UIManager:broadcastEvent(Event:new("Charging"))
 end
 
 -- The common operations that should be performed when the device is unplugged from a power source.
 function Device:_afterNotCharging()
-    -- Leave the kernel some time to figure it out ;o).
-    UIManager:scheduleIn(1, function() self:setupChargingLED() end)
+    self.powerd:invalidateCapacityCache()
+    self:_updateChargingLED()
     UIManager:broadcastEvent(Event:new("NotCharging"))
 end