Make method private to fix checkstyle error.

Checkstyle wants all public methods to have javadocs. Rather than add
javadocs for this method, mark it private, which is more appropriate.

Bug: 112431924
Test: atest RollbackTest
Change-Id: I438d16b0e4164482ba5f6527aecd50c65ce41418

tests/RollbackTest/TestApp/src/com/android/tests/rollback/testapp/CrashingMainActivity.java

@@ -33,7 +33,7 @@ public class CrashingMainActivity extends Activity {
         throw new RuntimeException("Intended force crash");
     }
 
-    public void incrementCountAndBroadcast() {
+    private void incrementCountAndBroadcast() {
         SharedPreferences preferences = getSharedPreferences("prefs", Context.MODE_PRIVATE);
         SharedPreferences.Editor editor = preferences.edit();
         int count = preferences.getInt("crash_count", 0);