Added test support to observe and verify UMA user actions during tests.

base/test/user_action_tester.cc

+// Copyright 2015 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 "base/test/user_action_tester.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/metrics/user_metrics.h"

[Mark Mentovai, 2015/04/13 20:08:37]

Me too.

+
+namespace base {
+
+UserActionTester::UserActionTester()
+    : action_callback_(
+          base::Bind(&UserActionTester::OnUserAction, base::Unretained(this))) {
+  base::AddActionCallback(action_callback_);
+}
+
+UserActionTester::~UserActionTester() {
+  base::RemoveActionCallback(action_callback_);
+}
+
+int UserActionTester::GetActionCount(const std::string& user_action) const {
+  UserActionCountMap::const_iterator iter = count_map_.find(user_action);
+  return iter == count_map_.end() ? 0 : iter->second;
+}
+
+void UserActionTester::ResetCounts() {
+  count_map_.clear();
+}
+
+void UserActionTester::OnUserAction(const std::string& user_action) {
+  ++(count_map_[user_action]);
+}
+
+}  // namespace base