ml: add generic metrics to machine learning service

Add generic metrics to machine learning service, to log event(success or
fail), time_cost, cpu_time_cost and memory_usage

BUG=chromium:892999
TEST=Tested with chromium browser by adding fake event in it and
monitoring the histograms

Change-Id: I3fbc364b18c21fd4f093427670624ced0dd1984b
Reviewed-on: https://chromium-review.googlesource.com/1312494
Commit-Ready: Xinglong Luan <alanlxl@chromium.org>
Tested-by: Xinglong Luan <alanlxl@chromium.org>
Reviewed-by: Andrew Moylan <amoylan@chromium.org>
diff --git a/ml/machine_learning_service_impl.h b/ml/machine_learning_service_impl.h
index 9025ac4..d7218a2 100644
--- a/ml/machine_learning_service_impl.h
+++ b/ml/machine_learning_service_impl.h
@@ -6,6 +6,7 @@
 #define ML_MACHINE_LEARNING_SERVICE_IMPL_H_
 
 #include <map>
+#include <memory>
 #include <string>
 
 #include <base/callback_forward.h>