Revert warning logic so it has a "don't show again" message.

BUG: 28140003

Change-Id: I93e7b1494a0f4c5ca080fbe9dd94dc2168092ffa
diff --git a/packages/Shell/src/com/android/shell/BugreportPrefs.java b/packages/Shell/src/com/android/shell/BugreportPrefs.java
index 3748e89..93690d4 100644
--- a/packages/Shell/src/com/android/shell/BugreportPrefs.java
+++ b/packages/Shell/src/com/android/shell/BugreportPrefs.java
@@ -22,22 +22,24 @@
 /**
  * Preferences related to bug reports.
  */
-public class BugreportPrefs {
-    private static final String PREFS_BUGREPORT = "bugreports";
+final class BugreportPrefs {
+    static final String PREFS_BUGREPORT = "bugreports";
 
     private static final String KEY_WARNING_STATE = "warning-state";
 
-    public static final int STATE_UNKNOWN = 0;
-    public static final int STATE_SHOW = 1;
-    public static final int STATE_HIDE = 2;
+    static final int STATE_UNKNOWN = 0;
+    // Shows the warning dialog.
+    static final int STATE_SHOW = 1;
+    // Skips the warning dialog.
+    static final int STATE_HIDE = 2;
 
-    public static int getWarningState(Context context, int def) {
+    static int getWarningState(Context context, int def) {
         final SharedPreferences prefs = context.getSharedPreferences(
                 PREFS_BUGREPORT, Context.MODE_PRIVATE);
         return prefs.getInt(KEY_WARNING_STATE, def);
     }
 
-    public static void setWarningState(Context context, int value) {
+    static void setWarningState(Context context, int value) {
         final SharedPreferences prefs = context.getSharedPreferences(
                 PREFS_BUGREPORT, Context.MODE_PRIVATE);
         prefs.edit().putInt(KEY_WARNING_STATE, value).apply();