Make SUBTYPE_UNKNOWN the first entry in ConnectionSubtype enum.

In https://codereview.chromium.org/1718943002 isherman pointed out that
it's preferable to make UNKNOWN the first entry in an enum. This change
updates ConnectionSubtype to make SUBTYPE_UNKNOWN the first entry.

BUG=589948

Review URL: https://codereview.chromium.org/1734873003

Cr-Commit-Position: refs/heads/master@{#377820}

net/base/network_change_notifier.h

@@ -66,7 +66,10 @@ class NET_EXPORT NetworkChangeNotifier {
   // A Java counterpart will be generated for this enum.
   // GENERATED_JAVA_ENUM_PACKAGE: org.chromium.net
   enum ConnectionSubtype {
-    SUBTYPE_GSM = 0,
+    SUBTYPE_UNKNOWN = 0,
+    SUBTYPE_NONE,
+    SUBTYPE_OTHER,
+    SUBTYPE_GSM,
     SUBTYPE_IDEN,
     SUBTYPE_CDMA,
     SUBTYPE_1XRTT,
@@ -96,10 +99,7 @@ class NET_EXPORT NetworkChangeNotifier {
     SUBTYPE_WIFI_N,
     SUBTYPE_WIFI_AC,
     SUBTYPE_WIFI_AD,
-    SUBTYPE_UNKNOWN,
-    SUBTYPE_NONE,
-    SUBTYPE_OTHER,
-    SUBTYPE_LAST = SUBTYPE_OTHER
+    SUBTYPE_LAST = SUBTYPE_WIFI_AD
   };
 
   class NET_EXPORT IPAddressObserver {