Fix message names in dumpsys network_stack

Constants were stripped out by ProGuard, so
MessageUtils.findMessageNames would fail to find them.

Test: flashed, dumpsys network_stack shows message names
Fixes: 124619824
Change-Id: I285ce2ab52cdff48f17b422285a635bd34243498

packages/NetworkStack/Android.bp

@@ -49,6 +49,9 @@ java_defaults {
     // Resources already included in NetworkStackBase
     resource_dirs: [],
     jarjar_rules: "jarjar-rules-shared.txt",
+    optimize: {
+        proguard_flags_files: ["proguard.flags"],
+    },
     // The permission configuration *must* be included to ensure security of the device
     required: ["NetworkStackPermissionStub"],
 }

packages/NetworkStack/proguard.flags

@@ -0,0 +1,9 @@
+-keepclassmembers class android.net.ip.IpClient {
+    static final int CMD_*;
+    static final int EVENT_*;
+}
+
+-keepclassmembers class android.net.dhcp.DhcpClient {
+    static final int CMD_*;
+    static final int EVENT_*;
+}

packages/NetworkStack/src/android/net/dhcp/DhcpClient.java

@@ -126,6 +126,7 @@ public class DhcpClient extends StateMachine {
     // DhcpClient uses IpClient's handler.
     private static final int PUBLIC_BASE = IpClient.DHCPCLIENT_CMD_BASE;
 
+    // Below constants are picked up by MessageUtils and exempt from ProGuard optimization.
     /* Commands from controller to start/stop DHCP */
     public static final int CMD_START_DHCP                  = PUBLIC_BASE + 1;
     public static final int CMD_STOP_DHCP                   = PUBLIC_BASE + 2;

packages/NetworkStack/src/android/net/ip/IpClient.java

@@ -282,6 +282,7 @@ public class IpClient extends StateMachine {
 
     public static final String DUMP_ARG_CONFIRM = "confirm";
 
+    // Below constants are picked up by MessageUtils and exempt from ProGuard optimization.
     private static final int CMD_TERMINATE_AFTER_STOP             = 1;
     private static final int CMD_STOP                             = 2;
     private static final int CMD_START                            = 3;