Fix bug and add logging in FalsingManager

Fixes bug that lead FalsingManager to be incorrect
about the screen on state.

Makes it a fatal error to query whether a touch is
falsing outside of an active session.

Prevents touch collection and logging on the locked
shade which needs no anti-falsing.

Bug: 27227578
Change-Id: I8e330ad28636156a952e61b8fe6a3d201f82e624
diff --git a/packages/SystemUI/src/com/android/systemui/classifier/Classifier.java b/packages/SystemUI/src/com/android/systemui/classifier/Classifier.java
index 89d20de..cb761a9 100644
--- a/packages/SystemUI/src/com/android/systemui/classifier/Classifier.java
+++ b/packages/SystemUI/src/com/android/systemui/classifier/Classifier.java
@@ -48,4 +48,6 @@
      */
     public void onSensorChanged(SensorEvent event) {
     }
+
+    public abstract String getTag();
 }