New javadoc for SysUI CoreStartables

Test: n/a
Bug: 259474752
Change-Id: Ide39a7bef9852980f5d8ad4c075edd0e4b53386b

packages/SystemUI/src/com/android/systemui/CoreStartable.java

@@ -39,10 +39,13 @@ import java.io.PrintWriter;
  */
 public interface CoreStartable extends Dumpable {
 
-    /** Main entry point for implementations. Called shortly after app startup. */
+    /** Main entry point for implementations. Called shortly after SysUI startup. */
     void start();
 
-    /** */
+    /** Called when the device configuration changes. This will not be called before
+     * {@link #start()}, but it could be called before {@link #onBootCompleted()}.
+     *
+     * @see android.app.Application#onConfigurationChanged(Configuration)  */
     default void onConfigurationChanged(Configuration newConfig) {
     }
 
@@ -50,7 +53,11 @@ public interface CoreStartable extends Dumpable {
     default void dump(@NonNull PrintWriter pw, @NonNull String[] args) {
     }
 
-    /** Called when the device reports BOOT_COMPLETED. */
+    /** Called immediately after the system broadcasts
+     * {@link android.content.Intent#ACTION_LOCKED_BOOT_COMPLETED} or during SysUI startup if the
+     * property {@code sys.boot_completed} is already set to 1. The latter typically occurs when
+     * starting a new SysUI instance, such as when starting SysUI for a secondary user.
+     * {@link #onBootCompleted()} will never be called before {@link #start()}. */
     default void onBootCompleted() {
     }
 }