gesture_log.py: AxisGesture: Add Distance accessor

Used by baseline regression tests

BUG=chromium:339347
TEST=Baseline test collection and replay works

Change-Id: Ideb434556c8864667f4304010e27b6359c94fb1c
Reviewed-on: https://chromium-review.googlesource.com/207712
Reviewed-by: Dennis Kempin <denniskempin@chromium.org>
Tested-by: Andrew de los Reyes <adlr@chromium.org>
Commit-Queue: Andrew de los Reyes <adlr@chromium.org>
diff --git a/mtlib/gesture_log.py b/mtlib/gesture_log.py
index 12939d9..5d2a42a 100755
--- a/mtlib/gesture_log.py
+++ b/mtlib/gesture_log.py
@@ -134,6 +134,9 @@
     self.segments.append(motion.distance)
     self.end = motion.end
 
+  def Distance(self):
+    return self.distance
+
   def Speed(self):
     """ Average speed of motion in mm/s. """
     if self.end > self.start: