Reapply "Adapt to libprocessgroup API changes for polling on cgro..."

This reverts commit 4a11b111.

This change was originally reverted due to a bug in the child commit of
a change in the same topic which caused process group kills not to occur
when using cgroup.kill. Now that has been fixed, bring back this change
with the fix.

Bug: 301871933
Change-Id: I81dde53f21ba2e01c01dfd5f7009ea1ef690b582

core/java/android/os/Process.java

@@ -1505,7 +1505,7 @@ public class Process {
      * fully removed, otherwise system resources may leak.
      * @hide
      */
-    public static final native int sendSignalToProcessGroup(int uid, int pid, int signal);
+    public static final native boolean sendSignalToProcessGroup(int uid, int pid, int signal);
 
     /**
       * Freeze the cgroup for the given UID.

core/jni/android_util_Process.cpp

@@ -1262,7 +1262,7 @@ jint android_os_Process_killProcessGroup(JNIEnv* env, jobject clazz, jint uid, j
     return killProcessGroup(uid, pid, SIGKILL);
 }
 
-jint android_os_Process_sendSignalToProcessGroup(JNIEnv* env, jobject clazz, jint uid, jint pid,
+jboolean android_os_Process_sendSignalToProcessGroup(JNIEnv* env, jobject clazz, jint uid, jint pid,
                                                  jint signal) {
     if (uid < 0) {
         return jniThrowExceptionFmt(env, "java/lang/IllegalArgumentException",
@@ -1344,7 +1344,7 @@ static const JNINativeMethod methods[] = {
         //{"setApplicationObject", "(Landroid/os/IBinder;)V",
         //(void*)android_os_Process_setApplicationObject},
         {"killProcessGroup", "(II)I", (void*)android_os_Process_killProcessGroup},
-        {"sendSignalToProcessGroup", "(III)I", (void*)android_os_Process_sendSignalToProcessGroup},
+        {"sendSignalToProcessGroup", "(III)Z", (void*)android_os_Process_sendSignalToProcessGroup},
         {"removeAllProcessGroups", "()V", (void*)android_os_Process_removeAllProcessGroups},
         {"nativePidFdOpen", "(II)I", (void*)android_os_Process_nativePidFdOpen},
         {"freezeCgroupUid", "(IZ)V", (void*)android_os_Process_freezeCgroupUID},