EventSequenceValidator: Only record the debug log in debugging level.

The stack trace log may confuse other developers and mistakenly points
to IORap as the bug cause.

Bug: 161145462
Test: Make and check the logcat.
Change-Id: I3cb24cace060cff381ab3c5770ff6c1c948a2d89

startop/iorap/src/com/google/android/startop/iorap/EventSequenceValidator.java

@@ -96,7 +96,8 @@ import java.io.PrintWriter;
  */
 public class EventSequenceValidator implements ActivityMetricsLaunchObserver {
   static final String TAG = "EventSequenceValidator";
-
+  /** $> adb shell 'setprop log.tag.EventSequenceValidator VERBOSE' */
+  public static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);
   private State state = State.INIT;
   private long accIntentStartedEvents = 0;
 
@@ -255,10 +256,12 @@ public class EventSequenceValidator implements ActivityMetricsLaunchObserver {
   }
 
   private void logWarningWithStackTrace(String log) {
-    StringWriter sw = new StringWriter();
-    PrintWriter pw = new PrintWriter(sw);
-    new Throwable("EventSequenceValidator#getStackTrace").printStackTrace(pw);
-    Log.wtf(TAG, String.format("%s\n%s", log, sw));
+    if (DEBUG) {
+      StringWriter sw = new StringWriter();
+      PrintWriter pw = new PrintWriter(sw);
+      new Throwable("EventSequenceValidator#getStackTrace").printStackTrace(pw);
+      Log.wtf(TAG, String.format("%s\n%s", log, sw));
+    }
   }
 }