Disable notification channel warnings by default

 * Since we usually ship "userdebug" builds, it is better to globally
   disable the toast because we are not in control of third-party apps
   that haven't been properly aligned with new Oreo requirements.

 * Leave it enabled by default only for "eng" builds

Issue: FP2A10-220
Change-Id: Ie5cdec1cbdd3285af3af730dac4a5de95ad8b334
(cherry picked from commit d16f2f86d7e4b79ec1505ab08ce793a5758d3d06)
(cherry picked from commit a1677f48c92be8fea7952da6f4c100d6ae104de1)
diff --git a/src/com/android/settings/development/NotificationChannelWarningsPreferenceController.java b/src/com/android/settings/development/NotificationChannelWarningsPreferenceController.java
index 775b708..104fcde 100644
--- a/src/com/android/settings/development/NotificationChannelWarningsPreferenceController.java
+++ b/src/com/android/settings/development/NotificationChannelWarningsPreferenceController.java
@@ -80,6 +80,6 @@
 
     @VisibleForTesting
     boolean isDebuggable() {
-        return Build.IS_DEBUGGABLE;
+        return Build.IS_ENG;
     }
 }