autotest: move or eliminate a bunch of autotest_stats stats

BUG=chromium:667171
TEST=Ran unittest & trybot success on x86-mario-paladin

Change-Id: Idaca9f54476bce76563671a85edf2f13c3e37b3a
Reviewed-on: https://chromium-review.googlesource.com/413294
Commit-Ready: Xixuan Wu <xixuan@chromium.org>
Tested-by: Xixuan Wu <xixuan@chromium.org>
Reviewed-by: Xixuan Wu <xixuan@chromium.org>
diff --git a/scheduler/rdb_cache_manager.py b/scheduler/rdb_cache_manager.py
index cd3cc17..2117750 100644
--- a/scheduler/rdb_cache_manager.py
+++ b/scheduler/rdb_cache_manager.py
@@ -81,10 +81,11 @@
 import logging
 
 import common
-from autotest_lib.client.common_lib.cros.graphite import autotest_stats
 from autotest_lib.client.common_lib.global_config import global_config
 from autotest_lib.scheduler import rdb_utils
 
+from chromite.lib import metrics
+
 MEMOIZE_KEY = 'memoized_hosts'
 
 def memoize_hosts(func):
@@ -233,10 +234,11 @@
         staleness = self.mean_staleness()
         logging.debug('Cache stats: hit ratio: %.2f%%, '
                       'avg staleness per line: %.2f%%.', hit_ratio, staleness)
-        autotest_stats.Gauge(rdb_utils.RDB_STATS_KEY).send(
-                'cache.hit_ratio', hit_ratio)
-        autotest_stats.Gauge(rdb_utils.RDB_STATS_KEY).send(
-                'cache.stale_entries', staleness)
+        metrics.Float('chromeos/autotest/scheduler/rdb/cache/hit_ratio').set(
+                hit_ratio)
+        metrics.Float(
+                'chromeos/autotest/scheduler/rdb/cache/mean_staleness').set(
+                        staleness)
 
 
     @classmethod