Widevine Metrics System

This change is the complete Widevine metrics system. It will
measure and record runtime information about what is happening
in the CDM - such as errors and throughput.

Bug: 33745339
Bug: 26027857
Change-Id: Ic9a82074f1e2b72c72d751b235f8ae361232787d

libwvdrmengine/cdm/metrics/src/distribution.cpp

@@ -0,0 +1,33 @@
+// Copyright 2017 Google Inc. All Rights Reserved.
+//
+// This file contains the definitions for the Distribution class members.
+
+#include "distribution.h"
+
+#include <float.h>
+
+namespace wvcdm {
+namespace metrics {
+
+Distribution::Distribution() :
+    count_(0LL),
+    min_(DBL_MAX),
+    max_(-DBL_MAX),
+    mean_(0.0),
+    sum_squared_deviation_(0.0) {
+}
+
+void Distribution::Record(double value) {
+  // Using method of provisional means.
+  double deviation = value - mean_;
+  mean_ = mean_ + (deviation / ++count_);
+  sum_squared_deviation_ =
+     sum_squared_deviation_ + (deviation * (value - mean_));
+
+  min_ = min_ < value ? min_ : value;
+  max_ = max_ > value ? max_ : value;
+}
+
+}  // namespace metrics
+}  // namespace wvcdm
+