Add a notification when console is active

Performance is largely impacted when console is running, and device
should not ship with that configuration. Moreover, we have seen cases,
when performance of new features was tested with UART on. This CL adds a
notification when console service is active indicating UART is on.

Fixes: 119623211
Test: Enable UART and see warning after boot
Test: Disable UART and no warning
Change-Id: Ie60f763088a15608027986ac855466eb7fc97264
diff --git a/proto/src/system_messages.proto b/proto/src/system_messages.proto
index ffbf1ae..5d6d1c9 100644
--- a/proto/src/system_messages.proto
+++ b/proto/src/system_messages.proto
@@ -230,6 +230,10 @@
     // Package: android
     NOTE_TEST_HARNESS_MODE_ENABLED = 54;
 
+    // Inform the user that Serial Console is active.
+    // Package: android
+    NOTE_SERIAL_CONSOLE_ENABLED = 55;
+
     // ADD_NEW_IDS_ABOVE_THIS_LINE
     // Legacy IDs with arbitrary values appear below
     // Legacy IDs existed as stable non-conflicting constants prior to the O release