Update from https://crrev.com/316786

base/metrics/stats_table.h

Index: base/metrics/stats_table.h
diff --git a/base/metrics/stats_table.h b/base/metrics/stats_table.h
deleted file mode 100644
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--- a/base/metrics/stats_table.h
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-// 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.
-//
-// A StatsTable is a table of statistics.  It can be used across multiple
-// processes and threads, maintaining cheap statistics counters without
-// locking.
-//
-// The goal is to make it very cheap and easy for developers to add
-// counters to code, without having to build one-off utilities or mechanisms
-// to track the counters, and also to allow a single "view" to display
-// the contents of all counters.
-//
-// To achieve this, StatsTable creates a shared memory segment to store
-// the data for the counters.  Upon creation, it has a specific size
-// which governs the maximum number of counters and concurrent
-// threads/processes which can use it.
-//
-
-#ifndef BASE_METRICS_STATS_TABLE_H_
-#define BASE_METRICS_STATS_TABLE_H_
-
-#include <string>
-
-#include "base/base_export.h"
-#include "base/basictypes.h"
-#include "base/containers/hash_tables.h"
-#include "base/memory/shared_memory.h"
-#include "base/synchronization/lock.h"
-#include "base/threading/thread_local_storage.h"
-#include "build/build_config.h"
-
-#if defined(OS_POSIX)
-#include "base/file_descriptor_posix.h"
-#endif
-
-namespace base {
-
-class BASE_EXPORT StatsTable {
- public:
-  // Identifies a StatsTable. We often want to share these between processes.
-  //
-  // On Windows, we use a named shared memory segment so the table identifier
-  // should be a relatively unique string identifying the table to use. An
-  // empty string can be used to use an anonymous shared memory segment for
-  // cases where the table does not need to be shared between processes.
-  //
-  // Posix does not support named memory so we explicitly share file
-  // descriptors. On Posix, pass a default-constructed file descriptor if a
-  // handle doesn't already exist, and a new one will be created.
-  //
-  // If a table doesn't already exist with the given identifier, a new one will
-  // be created with zeroed counters.
-#if defined(OS_POSIX)
-  typedef FileDescriptor TableIdentifier;
-#elif defined(OS_WIN)
-  typedef std::string TableIdentifier;
-#endif
-
-  // Create a new StatsTable.
-  //
-  // max_threads is the maximum number of threads the table will support.
-  // If the StatsTable already exists, this number is ignored.
-  //
-  // max_counters is the maximum number of counters the table will support.
-  // If the StatsTable already exists, this number is ignored.
-  StatsTable(const TableIdentifier& table,
-             int max_threads,
-             int max_counters);
-
-  // Destroys the StatsTable.  When the last StatsTable is destroyed
-  // (across all processes), the StatsTable is removed from disk.
-  ~StatsTable();
-
-  // For convenience, we create a static table.  This is generally
-  // used automatically by the counters.
-  static StatsTable* current();
-
-  // Set the global table for use in this process.
-  static void set_current(StatsTable* value);
-
-  // Get the slot id for the calling thread. Returns 0 if no
-  // slot is assigned.
-  int GetSlot() const;
-
-  // All threads that contribute data to the table must register with the
-  // table first.  This function will set thread local storage for the
-  // thread containing the location in the table where this thread will
-  // write its counter data.
-  //
-  // name is just a debugging tag to label the thread, and it does not
-  // need to be unique.  It will be truncated to kMaxThreadNameLength-1
-  // characters.
-  //
-  // On success, returns the slot id for this thread.  On failure,
-  // returns 0.
-  int RegisterThread(const std::string& name);
-
-  // Returns the number of threads currently registered.  This is really not
-  // useful except for diagnostics and debugging.
-  int CountThreadsRegistered() const;
-
-  // Find a counter in the StatsTable.
-  //
-  // Returns an id for the counter which can be used to call GetLocation().
-  // If the counter does not exist, attempts to create a row for the new
-  // counter.  If there is no space in the table for the new counter,
-  // returns 0.
-  int FindCounter(const std::string& name);
-
-  // TODO(mbelshe): implement RemoveCounter.
-
-  // Gets the location of a particular value in the table based on
-  // the counter id and slot id.
-  int* GetLocation(int counter_id, int slot_id) const;
-
-  // Gets the counter name at a particular row.  If the row is empty,
-  // returns NULL.
-  const char* GetRowName(int index) const;
-
-  // Gets the sum of the values for a particular row.
-  int GetRowValue(int index) const;
-
-  // Gets the sum of the values for a particular row for a given pid.
-  int GetRowValue(int index, int pid) const;
-
-  // Gets the sum of the values for a particular counter.  If the counter
-  // does not exist, creates the counter.
-  int GetCounterValue(const std::string& name);
-
-  // Gets the sum of the values for a particular counter for a given pid.
-  // If the counter does not exist, creates the counter.
-  int GetCounterValue(const std::string& name, int pid);
-
-  // The maxinum number of counters/rows in the table.
-  int GetMaxCounters() const;
-
-  // The maxinum number of threads/columns in the table.
-  int GetMaxThreads() const;
-
-#if defined(OS_POSIX)
-  // Get the underlying shared memory handle for the table.
-  base::SharedMemoryHandle GetSharedMemoryHandle() const;
-#endif
-
-  // The maximum length (in characters) of a Thread's name including
-  // null terminator, as stored in the shared memory.
-  static const int kMaxThreadNameLength = 32;
-
-  // The maximum length (in characters) of a Counter's name including
-  // null terminator, as stored in the shared memory.
-  static const int kMaxCounterNameLength = 64;
-
-  // Convenience function to lookup a counter location for a
-  // counter by name for the calling thread.  Will register
-  // the thread if it is not already registered.
-  static int* FindLocation(const char *name);
-
- private:
-  class Internal;
-  struct TLSData;
-  typedef hash_map<std::string, int> CountersMap;
-
-  // Returns the space occupied by a thread in the table.  Generally used
-  // if a thread terminates but the process continues.  This function
-  // does not zero out the thread's counters.
-  // Cannot be used inside a posix tls destructor.
-  void UnregisterThread();
-
-  // This variant expects the tls data to be passed in, so it is safe to
-  // call from inside a posix tls destructor (see doc for pthread_key_create).
-  void UnregisterThread(TLSData* tls_data);
-
-  // The SlotReturnFunction is called at thread exit for each thread
-  // which used the StatsTable.
-  static void SlotReturnFunction(void* data);
-
-  // Locates a free slot in the table.  Returns a number > 0 on success,
-  // or 0 on failure.  The caller must hold the shared_memory lock when
-  // calling this function.
-  int FindEmptyThread() const;
-
-  // Locates a counter in the table or finds an empty row.  Returns a
-  // number > 0 on success, or 0 on failure.  The caller must hold the
-  // shared_memory_lock when calling this function.
-  int FindCounterOrEmptyRow(const std::string& name) const;
-
-  // Internal function to add a counter to the StatsTable.  Assumes that
-  // the counter does not already exist in the table.
-  //
-  // name is a unique identifier for this counter, and will be truncated
-  // to kMaxCounterNameLength-1 characters.
-  //
-  // On success, returns the counter_id for the newly added counter.
-  // On failure, returns 0.
-  int AddCounter(const std::string& name);
-
-  // Get the TLS data for the calling thread.  Returns NULL if none is
-  // initialized.
-  TLSData* GetTLSData() const;
-
-  Internal* internal_;
-
-  // The counters_lock_ protects the counters_ hash table.
-  base::Lock counters_lock_;
-
-  // The counters_ hash map is an in-memory hash of the counters.
-  // It is used for quick lookup of counters, but is cannot be used
-  // as a substitute for what is in the shared memory.  Even though
-  // we don't have a counter in our hash table, another process may
-  // have created it.
-  CountersMap counters_;
-  ThreadLocalStorage::Slot tls_index_;
-
-  DISALLOW_COPY_AND_ASSIGN(StatsTable);
-};
-
-}  // namespace base
-
-#endif  // BASE_METRICS_STATS_TABLE_H_