Add the WebRTC.webkitApiCountPerSession metric.

content/renderer/media/webrtc_uma_histograms.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/renderer/media/webrtc_uma_histograms.h"
+
+#include "base/metrics/histogram.h"
+
+namespace content {
+
+void UpdateWebRTCMethodCount(JavaScriptAPIName api_name) {
+  DVLOG(3) << "Incrementing WebRTC.webkitApiCount for " << api_name;
+  UMA_HISTOGRAM_ENUMERATION("WebRTC.webkitApiCount", api_name, INVALID_NAME);
+  PerSessionWebRTCAPIMetrics::GetInstance()->LogUsageOnlyOnce(api_name);
+}
+
+PerSessionWebRTCAPIMetrics::~PerSessionWebRTCAPIMetrics() {
+}
+
+// static
+PerSessionWebRTCAPIMetrics* PerSessionWebRTCAPIMetrics::GetInstance() {
+  return Singleton<PerSessionWebRTCAPIMetrics>::get();
+}
+
+void PerSessionWebRTCAPIMetrics::IncrementStreamCounter() {
+  DCHECK(CalledOnValidThread());
+  ++num_streams_;
+}
+
+void PerSessionWebRTCAPIMetrics::DecrementStreamCounter() {
+  DCHECK(CalledOnValidThread());
+  if (--num_streams_ == 0) {
+    ResetUsage();
+  }
+}
+
+PerSessionWebRTCAPIMetrics::PerSessionWebRTCAPIMetrics() : num_streams_(0) {
+  ResetUsage();
+}
+
+void PerSessionWebRTCAPIMetrics::LogUsage(JavaScriptAPIName api_name) {
+  DVLOG(3) << "Incrementing WebRTC.webkitApiCountPerSession for " << api_name;
+  UMA_HISTOGRAM_ENUMERATION("WebRTC.webkitApiCountPerSession",
+                            api_name, INVALID_NAME);
+}
+
+void PerSessionWebRTCAPIMetrics::LogUsageOnlyOnce(JavaScriptAPIName api_name) {
+  DCHECK(CalledOnValidThread());
+  if (!has_used_api_[api_name]) {
+    has_used_api_[api_name] = true;
+    LogUsage(api_name);
+  }
+}
+
+void PerSessionWebRTCAPIMetrics::ResetUsage() {
+  for (size_t i = 0; i < arraysize(has_used_api_); ++i)
+    has_used_api_[i] = false;
+}
+
+}  // namespace content