AlarmManagerService: add tracing for wakeup alarms

Test: tracepoints work
bug 69862220

Change-Id: Iba77129162958556aec7efd36e485fab6e6857ec
diff --git a/services/core/java/com/android/server/AlarmManagerService.java b/services/core/java/com/android/server/AlarmManagerService.java
index 3904fc9..ab252a4 100644
--- a/services/core/java/com/android/server/AlarmManagerService.java
+++ b/services/core/java/com/android/server/AlarmManagerService.java
@@ -49,6 +49,7 @@
 import android.os.ServiceManager;
 import android.os.SystemClock;
 import android.os.SystemProperties;
+import android.os.Trace;
 import android.os.UserHandle;
 import android.os.WorkSource;
 import android.provider.Settings;
@@ -3073,6 +3074,11 @@
         for (int i=0; i<triggerList.size(); i++) {
             Alarm alarm = triggerList.get(i);
             final boolean allowWhileIdle = (alarm.flags&AlarmManager.FLAG_ALLOW_WHILE_IDLE) != 0;
+            if (alarm.wakeup) {
+              Trace.traceBegin(Trace.TRACE_TAG_POWER, "Dispatch wakeup alarm to " + alarm.packageName);
+            } else {
+              Trace.traceBegin(Trace.TRACE_TAG_POWER, "Dispatch non-wakeup alarm to " + alarm.packageName);
+            }
             try {
                 if (localLOGV) {
                     Slog.v(TAG, "sending alarm " + alarm);
@@ -3092,6 +3098,7 @@
             } catch (RuntimeException e) {
                 Slog.w(TAG, "Failure sending alarm.", e);
             }
+            Trace.traceEnd(Trace.TRACE_TAG_POWER);
         }
     }