Add FrameworkStatsdTest to mainline test mapping for Statsd.

Bug: 185458355
Test: unittest
      forrest
Change-Id: I7231a8fabdbdd6ca6899924d60061735c50f032c
diff --git a/apex/TEST_MAPPING b/apex/TEST_MAPPING
index 331fe77..0d3770f 100644
--- a/apex/TEST_MAPPING
+++ b/apex/TEST_MAPPING
@@ -1,4 +1,9 @@
 {
+  "mainline-presubmit" : [
+    {
+      "name" : "FrameworkStatsdTest[com.google.android.os.statsd.apex]"
+    }
+  ],
   "presubmit" : [
     {
       "name" : "FrameworkStatsdTest"