Add tests for control message length

This will avoid regressions for #1245.

<https://github.com/Genymobile/scrcpy/issues/1245>

server/src/main/java/com/genymobile/scrcpy/ControlMessageReader.java

@@ -8,10 +8,10 @@ import java.nio.charset.StandardCharsets;
 
 public class ControlMessageReader {
 
-    private static final int INJECT_KEYCODE_PAYLOAD_LENGTH = 9;
-    private static final int INJECT_TOUCH_EVENT_PAYLOAD_LENGTH = 27;
-    private static final int INJECT_SCROLL_EVENT_PAYLOAD_LENGTH = 20;
-    private static final int SET_SCREEN_POWER_MODE_PAYLOAD_LENGTH = 1;
+    static final int INJECT_KEYCODE_PAYLOAD_LENGTH = 9;
+    static final int INJECT_TOUCH_EVENT_PAYLOAD_LENGTH = 27;
+    static final int INJECT_SCROLL_EVENT_PAYLOAD_LENGTH = 20;
+    static final int SET_SCREEN_POWER_MODE_PAYLOAD_LENGTH = 1;
 
     public static final int TEXT_MAX_LENGTH = 300;
     public static final int CLIPBOARD_TEXT_MAX_LENGTH = 4093;

server/src/test/java/com/genymobile/scrcpy/ControlMessageReaderTest.java

@@ -28,6 +28,9 @@ public class ControlMessageReaderTest {
         dos.writeInt(KeyEvent.META_CTRL_ON);
         byte[] packet = bos.toByteArray();
 
+        // The message type (1 byte) does not count
+        Assert.assertEquals(ControlMessageReader.INJECT_KEYCODE_PAYLOAD_LENGTH, packet.length - 1);
+
         reader.readFrom(new ByteArrayInputStream(packet));
         ControlMessage event = reader.next();
 
@@ -95,6 +98,9 @@ public class ControlMessageReaderTest {
 
         byte[] packet = bos.toByteArray();
 
+        // The message type (1 byte) does not count
+        Assert.assertEquals(ControlMessageReader.INJECT_TOUCH_EVENT_PAYLOAD_LENGTH, packet.length - 1);
+
         reader.readFrom(new ByteArrayInputStream(packet));
         ControlMessage event = reader.next();
 
@@ -126,6 +132,9 @@ public class ControlMessageReaderTest {
 
         byte[] packet = bos.toByteArray();
 
+        // The message type (1 byte) does not count
+        Assert.assertEquals(ControlMessageReader.INJECT_SCROLL_EVENT_PAYLOAD_LENGTH, packet.length - 1);
+
         reader.readFrom(new ByteArrayInputStream(packet));
         ControlMessage event = reader.next();
 
@@ -233,6 +242,9 @@ public class ControlMessageReaderTest {
 
         byte[] packet = bos.toByteArray();
 
+        // The message type (1 byte) does not count
+        Assert.assertEquals(ControlMessageReader.SET_SCREEN_POWER_MODE_PAYLOAD_LENGTH, packet.length - 1);
+
         reader.readFrom(new ByteArrayInputStream(packet));
         ControlMessage event = reader.next();