Notify the policy when a stylus gesture starts

This will serve as a hint to the policy that a stylus is currently being
used.

Bug: 243005009
Test: atest inputflinger_tests
Change-Id: I2cc187af226fc3a1d4fda36becc280ea7934673a
diff --git a/services/inputflinger/include/InputReaderBase.h b/services/inputflinger/include/InputReaderBase.h
index cacb63c..8c586b5 100644
--- a/services/inputflinger/include/InputReaderBase.h
+++ b/services/inputflinger/include/InputReaderBase.h
@@ -393,6 +393,8 @@
     /* Gets the affine calibration associated with the specified device. */
     virtual TouchAffineTransformation getTouchAffineTransformation(
             const std::string& inputDeviceDescriptor, int32_t surfaceRotation) = 0;
+    /* Notifies the input reader policy that a stylus gesture has started. */
+    virtual void notifyStylusGestureStarted(int32_t deviceId, nsecs_t eventTime) = 0;
 };
 
 } // namespace android