update_engine: Convert NetworkConnectionType to enum class.

This patch simply converts the old NetworkConnectionType enum to an
enum class and updates all the callsites and formatting.

BUG=None
TEST=emerge-link update_engine.

Change-Id: I29a281f1648e2d8ef74b1046d01a212022280461
Reviewed-on: https://chromium-review.googlesource.com/289585
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
Trybot-Ready: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
Trybot-Ready: Prathmesh Prabhu <pprabhu@chromium.org>
diff --git a/utils.cc b/utils.cc
index 97ce712..7777fca 100644
--- a/utils.cc
+++ b/utils.cc
@@ -1240,32 +1240,33 @@
     NetworkConnectionType type,
     NetworkTethering tethering) {
   switch (type) {
-    case kNetUnknown:
+    case NetworkConnectionType::kUnknown:
       return metrics::ConnectionType::kUnknown;
 
-    case kNetEthernet:
+    case NetworkConnectionType::kEthernet:
       if (tethering == NetworkTethering::kConfirmed)
         return metrics::ConnectionType::kTetheredEthernet;
       else
         return metrics::ConnectionType::kEthernet;
 
-    case kNetWifi:
+    case NetworkConnectionType::kWifi:
       if (tethering == NetworkTethering::kConfirmed)
         return metrics::ConnectionType::kTetheredWifi;
       else
         return metrics::ConnectionType::kWifi;
 
-    case kNetWimax:
+    case NetworkConnectionType::kWimax:
       return metrics::ConnectionType::kWimax;
 
-    case kNetBluetooth:
+    case NetworkConnectionType::kBluetooth:
       return metrics::ConnectionType::kBluetooth;
 
-    case kNetCellular:
+    case NetworkConnectionType::kCellular:
       return metrics::ConnectionType::kCellular;
   }
 
-  LOG(ERROR) << "Unexpected network connection type: type=" << type
+  LOG(ERROR) << "Unexpected network connection type: type="
+             << static_cast<int>(type)
              << ", tethering=" << static_cast<int>(tethering);
 
   return metrics::ConnectionType::kUnknown;