Better ConnectivityMetricsEvent printing

This patch adds more information printing for IpConnectivity event
classes in android.net.metrics.

example:

ConnectivityMetricsEvent(14:36:35.799, 0, 1026): DhcpClientEvent(wlan0, DhcpRequestingState)
ConnectivityMetricsEvent(14:36:35.805, 0, 1026): DhcpClientEvent(wlan0, DhcpHaveAddressState)
ConnectivityMetricsEvent(14:36:35.809, 0, 4096): IpManagerEvent(wlan0, PROVISIONING_OK, 155ms)
ConnectivityMetricsEvent(14:36:35.810, 0, 1026): DhcpClientEvent(wlan0, DhcpBoundState)
ConnectivityMetricsEvent(14:36:35.871, 0, 2048): NetworkEvent(101, NETWORK_CONNECTED, 0ms)
ConnectivityMetricsEvent(14:36:35.874, 0, 2051): ValidationProbeEvent(101, PROBE_HTTP:599, 3ms)
ConnectivityMetricsEvent(14:36:35.874, 0, 2048): NetworkEvent(101, NETWORK_VALIDATION_FAILED, 0ms)
ConnectivityMetricsEvent(14:36:35.928, 0, 3072): DefaultNetworkEvent(0 -> 101, [WIFI], IPv4: false, IPv6: false)
ConnectivityMetricsEvent(14:36:37.008, 0, 2051): ValidationProbeEvent(101, PROBE_HTTP:204, 134ms)
ConnectivityMetricsEvent(14:36:37.008, 0, 2050): NetworkEvent(101, NETWORK_VALIDATED, 1137ms)

Also fixes a couple of event logging issues:
  - do no record spurious receive DhcpErrorEvent when a network goes down.
  - add an eventType field to IpManagerEvent instead of using the
    loggger component tag.

Bug: 28204408
Change-Id: Ia6f4ccfd7a0c63a5ccec18825f226c0b5781217b
diff --git a/core/java/android/net/NetworkCapabilities.java b/core/java/android/net/NetworkCapabilities.java
index 64186145..6243f46 100644
--- a/core/java/android/net/NetworkCapabilities.java
+++ b/core/java/android/net/NetworkCapabilities.java
@@ -809,17 +809,7 @@
     @Override
     public String toString() {
         int[] types = getTransportTypes();
-        String transports = (types.length > 0 ? " Transports: " : "");
-        for (int i = 0; i < types.length;) {
-            switch (types[i]) {
-                case TRANSPORT_CELLULAR:    transports += "CELLULAR"; break;
-                case TRANSPORT_WIFI:        transports += "WIFI"; break;
-                case TRANSPORT_BLUETOOTH:   transports += "BLUETOOTH"; break;
-                case TRANSPORT_ETHERNET:    transports += "ETHERNET"; break;
-                case TRANSPORT_VPN:         transports += "VPN"; break;
-            }
-            if (++i < types.length) transports += "|";
-        }
+        String transports = (types.length > 0) ? " Transports: " + transportNamesOf(types) : "";
 
         types = getCapabilities();
         String capabilities = (types.length > 0 ? " Capabilities: " : "");
@@ -859,4 +849,22 @@
 
         return "[" + transports + capabilities + upBand + dnBand + specifier + signalStrength + "]";
     }
+
+    /**
+     * @hide
+     */
+    public static String transportNamesOf(int[] types) {
+        String transports = "";
+        for (int i = 0; i < types.length;) {
+            switch (types[i]) {
+                case TRANSPORT_CELLULAR:    transports += "CELLULAR"; break;
+                case TRANSPORT_WIFI:        transports += "WIFI"; break;
+                case TRANSPORT_BLUETOOTH:   transports += "BLUETOOTH"; break;
+                case TRANSPORT_ETHERNET:    transports += "ETHERNET"; break;
+                case TRANSPORT_VPN:         transports += "VPN"; break;
+            }
+            if (++i < types.length) transports += "|";
+        }
+        return transports;
+    }
 }