Split UserMetrics into API vs. implementation. Move API to content/public.

content/browser/user_metrics.h

-// Copyright (c) 2011 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.
-
-#ifndef CONTENT_BROWSER_USER_METRICS_H_
-#define CONTENT_BROWSER_USER_METRICS_H_
-#pragma once
-
-#include <string>
-
-#include "content/common/content_export.h"
-
-// This module provides some helper functions for logging actions tracked by
-// the user metrics system.
-
-
-// UserMetricsAction exist purely to standardize on the paramters passed to
-// UserMetrics. That way, our toolset can scan the sourcecode reliable for
-// constructors and extract the associated string constants
-struct UserMetricsAction {
-  const char* str_;
-  explicit UserMetricsAction(const char* str) : str_(str) {}
-};
-
-
-class CONTENT_EXPORT UserMetrics {
- public:
-  // Record that the user performed an action.
-  // "Action" here means a user-generated event:
-  //   good: "Reload", "CloseTab", and "IMEInvoked"
-  //   not good: "SSLDialogShown", "PageLoaded", "DiskFull"
-  // We use this to gather anonymized information about how users are
-  // interacting with the browser.
-  // WARNING: Call this function exactly like this:
-  //   UserMetrics::RecordAction(UserMetricsAction("foo bar"));
-  // (all on one line and with the metric string literal [no variables])
-  // because otherwise our processing scripts won't pick up on new actions.
-  //
-  // Once a new recorded action is added, run chrome/tools/extract_actions.py
-  // to generate a new mapping of [action hashes -> metric names] and send it
-  // out for review to be updated.
-  //
-  // For more complicated situations (like when there are many different
-  // possible actions), see RecordComputedAction.
-  static void RecordAction(const UserMetricsAction& action);
-
-  // This function has identical input and behavior to RecordAction, but is
-  // not automatically found by the action-processing scripts.  It can be used
-  // when it's a pain to enumerate all possible actions, but if you use this
-  // you need to also update the rules for extracting known actions in
-  // chrome/tools/extract_actions.py.
-  static void RecordComputedAction(const std::string& action);
-
- private:
-  static void Record(const char *action);
-  static void CallRecordOnUI(const std::string& action);
-};
-
-#endif  // CONTENT_BROWSER_USER_METRICS_H_