Parse -1 as WARNING_DISABLED in NetworkPolicyManager.

Bug: 26934313
Bug: 31437693
Test: Flashed phone with new config (-1) and verified data warning is
disabled out of box.
Change-Id: Iabdfb9d0625698d525d7537a93b936df505bd0ab
diff --git a/services/core/java/com/android/server/net/NetworkPolicyManagerService.java b/services/core/java/com/android/server/net/NetworkPolicyManagerService.java
index 53dbed2..3e1c529 100644
--- a/services/core/java/com/android/server/net/NetworkPolicyManagerService.java
+++ b/services/core/java/com/android/server/net/NetworkPolicyManagerService.java
@@ -1442,8 +1442,14 @@
                 + "; generating default policy");
 
         // Build default mobile policy, and assume usage cycle starts today
-        final long warningBytes = mContext.getResources().getInteger(
-                com.android.internal.R.integer.config_networkPolicyDefaultWarning) * MB_IN_BYTES;
+        final int dataWarningConfig = mContext.getResources().getInteger(
+                com.android.internal.R.integer.config_networkPolicyDefaultWarning);
+        final long warningBytes;
+        if (dataWarningConfig == WARNING_DISABLED) {
+            warningBytes = WARNING_DISABLED;
+        } else {
+            warningBytes = dataWarningConfig * MB_IN_BYTES;
+        }
 
         final Time time = new Time();
         time.setToNow();