logcat: add 'kernel' to defaults

I'm asked at least once a week or more why a new service isn't starting.
Usually, the reason is that "File ... has incorrect label or no domain
transition from ... to another SELinux domain defined. ..." from init.
Even in permissive mode, this is required.

Bug: 63014404
Test: boot, check logcat
Change-Id: I7244a56fc46f84e9592e1eccf2d23461691965b3
diff --git a/logcat/logcat.cpp b/logcat/logcat.cpp
index 15e07fe..6e38d95 100644
--- a/logcat/logcat.cpp
+++ b/logcat/logcat.cpp
@@ -483,7 +483,8 @@
                     "                  Additionally, 'kernel' for userdebug and eng builds, and\n"
                     "                  'security' for Device Owner installations.\n"
                     "                  Multiple -b parameters or comma separated list of buffers are\n"
-                    "                  allowed. Buffers interleaved. Default -b main,system,crash.\n"
+                    "                  allowed. Buffers interleaved.\n"
+                    "                  Default -b main,system,crash,kernel.\n"
                     "  -B, --binary    Output the log in binary.\n"
                     "  -S, --statistics                       Output statistics.\n"
                     "  -p, --prune     Print prune white and ~black list. Service is specified as\n"
@@ -1312,6 +1313,10 @@
             dev = dev->next = new log_device_t("crash", false);
             context->devCount++;
         }
+        if (android_name_to_log_id("kernel") == LOG_ID_KERNEL) {
+            dev = dev->next = new log_device_t("kernel", false);
+            context->devCount++;
+        }
     }
 
     if (!!context->logRotateSizeKBytes && !context->outputFileName) {