Add a thread group for RT apps

This will be used to provide minimum capacity guarantees to RT tasks
sensitive to frequency drops such as synthesizer workloads.

Bug: 33085313

Change-Id: I3f50ead5aaf496bb55cdb2426f22225a3d6c94ed
Signed-off-by: Joel Fernandes <joelaf@google.com>

core/java/android/os/Process.java

@@ -386,6 +386,12 @@ public class Process {
      **/
     public static final int THREAD_GROUP_TOP_APP = 5;
 
+    /**
+     * Thread group for RT app.
+     * @hide
+     **/
+    public static final int THREAD_GROUP_RT_APP = 6;
+
     public static final int SIGNAL_QUIT = 3;
     public static final int SIGNAL_KILL = 9;
     public static final int SIGNAL_USR1 = 10;