[smart-charging] Add a field to UserChargingEvent

Add an additional field to UserChargingEvent.

Bug: 1028853
Change-Id: Icffeba88fa2ac949defd8b564f9420b2e0f40149
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1983118Reviewed-by: Jia Meng <jiameng@chromium.org>
Commit-Queue: Thanh Nguyen <thanhdng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#727932}

chrome/browser/chromeos/power/smart_charging/user_charging_event.proto

@@ -89,6 +89,9 @@ message UserChargingEvent {
     optional int32 screen_brightness_percent = 19;
     // Charge voltage in mV.
     optional int32 voltage = 20;
+    // Whether there's any shutdown/suspend action between the last charge
+    // and current event.
+    optional bool halt_from_last_charge = 21;
   }
 
   message Event {