Update from https://crrev.com/304418

base/metrics/histogram_macros.h

Index: base/metrics/histogram_macros.h
diff --git a/base/metrics/histogram_macros.h b/base/metrics/histogram_macros.h
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+// 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.
+
+#ifndef BASE_METRICS_HISTOGRAM_MACROS_H_
+#define BASE_METRICS_HISTOGRAM_MACROS_H_
+
+#include "base/atomicops.h"
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "base/metrics/histogram.h"
+#include "base/time/time.h"
+
+//------------------------------------------------------------------------------
+// Histograms are often put in areas where they are called many many times, and
+// performance is critical.  As a result, they are designed to have a very low
+// recurring cost of executing (adding additional samples).  Toward that end,
+// the macros declare a static pointer to the histogram in question, and only
+// take a "slow path" to construct (or find) the histogram on the first run
+// through the macro.  We leak the histograms at shutdown time so that we don't
+// have to validate using the pointers at any time during the running of the
+// process.
+
+// The following code is generally what a thread-safe static pointer
+// initialization looks like for a histogram (after a macro is expanded).  This
+// sample is an expansion (with comments) of the code for
+// LOCAL_HISTOGRAM_CUSTOM_COUNTS().
+
+/*
+  do {
+    // The pointer's presence indicates the initialization is complete.
+    // Initialization is idempotent, so it can safely be atomically repeated.
+    static base::subtle::AtomicWord atomic_histogram_pointer = 0;
+
+    // Acquire_Load() ensures that we acquire visibility to the pointed-to data
+    // in the histogram.
+    base::Histogram* histogram_pointer(reinterpret_cast<base::Histogram*>(
+        base::subtle::Acquire_Load(&atomic_histogram_pointer)));
+
+    if (!histogram_pointer) {
+      // This is the slow path, which will construct OR find the matching
+      // histogram.  FactoryGet includes locks on a global histogram name map
+      // and is completely thread safe.
+      histogram_pointer = base::Histogram::FactoryGet(
+          name, min, max, bucket_count, base::HistogramBase::kNoFlags);
+
+      // Use Release_Store to ensure that the histogram data is made available
+      // globally before we make the pointer visible.
+      // Several threads may perform this store, but the same value will be
+      // stored in all cases (for a given named/spec'ed histogram).
+      // We could do this without any barrier, since FactoryGet entered and
+      // exited a lock after construction, but this barrier makes things clear.
+      base::subtle::Release_Store(&atomic_histogram_pointer,
+          reinterpret_cast<base::subtle::AtomicWord>(histogram_pointer));
+    }
+
+    // Ensure calling contract is upheld, and the name does NOT vary.
+    DCHECK(histogram_pointer->histogram_name() == constant_histogram_name);
+
+    histogram_pointer->Add(sample);
+  } while (0);
+*/
+
+// The above pattern is repeated in several macros.  The only elements that
+// vary are the invocation of the Add(sample) vs AddTime(sample), and the choice
+// of which FactoryGet method to use.  The different FactoryGet methods have
+// various argument lists, so the function with its argument list is provided as
+// a macro argument here.  The name is only used in a DCHECK, to assure that
+// callers don't try to vary the name of the histogram (which would tend to be
+// ignored by the one-time initialization of the histogtram_pointer).
+#define STATIC_HISTOGRAM_POINTER_BLOCK(constant_histogram_name, \
+                                       histogram_add_method_invocation, \
+                                       histogram_factory_get_invocation) \
+  do { \
+    static base::subtle::AtomicWord atomic_histogram_pointer = 0; \
+    base::HistogramBase* histogram_pointer( \
+        reinterpret_cast<base::HistogramBase*>( \
+            base::subtle::Acquire_Load(&atomic_histogram_pointer))); \
+    if (!histogram_pointer) { \
+      histogram_pointer = histogram_factory_get_invocation; \
+      base::subtle::Release_Store(&atomic_histogram_pointer, \
+          reinterpret_cast<base::subtle::AtomicWord>(histogram_pointer)); \
+    } \
+    if (DCHECK_IS_ON) \
+      histogram_pointer->CheckName(constant_histogram_name); \
+    histogram_pointer->histogram_add_method_invocation; \
+  } while (0)
+
+
+//------------------------------------------------------------------------------
+// Provide easy general purpose histogram in a macro, just like stats counters.
+// The first four macros use 50 buckets.
+
+#define LOCAL_HISTOGRAM_TIMES(name, sample) LOCAL_HISTOGRAM_CUSTOM_TIMES( \
+    name, sample, base::TimeDelta::FromMilliseconds(1), \
+    base::TimeDelta::FromSeconds(10), 50)
+
+// For folks that need real specific times, use this to select a precise range
+// of times you want plotted, and the number of buckets you want used.
+#define LOCAL_HISTOGRAM_CUSTOM_TIMES(name, sample, min, max, bucket_count) \
+    STATIC_HISTOGRAM_POINTER_BLOCK(name, AddTime(sample), \
+        base::Histogram::FactoryTimeGet(name, min, max, bucket_count, \
+                                        base::HistogramBase::kNoFlags))
+
+#define LOCAL_HISTOGRAM_COUNTS(name, sample) LOCAL_HISTOGRAM_CUSTOM_COUNTS( \
+    name, sample, 1, 1000000, 50)
+
+#define LOCAL_HISTOGRAM_COUNTS_100(name, sample) \
+    LOCAL_HISTOGRAM_CUSTOM_COUNTS(name, sample, 1, 100, 50)
+
+#define LOCAL_HISTOGRAM_COUNTS_10000(name, sample) \
+    LOCAL_HISTOGRAM_CUSTOM_COUNTS(name, sample, 1, 10000, 50)
+
+#define LOCAL_HISTOGRAM_CUSTOM_COUNTS(name, sample, min, max, bucket_count) \
+    STATIC_HISTOGRAM_POINTER_BLOCK(name, Add(sample), \
+        base::Histogram::FactoryGet(name, min, max, bucket_count, \
+                                    base::HistogramBase::kNoFlags))
+
+// This is a helper macro used by other macros and shouldn't be used directly.
+#define HISTOGRAM_ENUMERATION_WITH_FLAG(name, sample, boundary, flag) \
+    STATIC_HISTOGRAM_POINTER_BLOCK(name, Add(sample), \
+        base::LinearHistogram::FactoryGet(name, 1, boundary, boundary + 1, \
+            flag))
+
+#define LOCAL_HISTOGRAM_PERCENTAGE(name, under_one_hundred) \
+    LOCAL_HISTOGRAM_ENUMERATION(name, under_one_hundred, 101)
+
+#define LOCAL_HISTOGRAM_BOOLEAN(name, sample) \
+    STATIC_HISTOGRAM_POINTER_BLOCK(name, AddBoolean(sample), \
+        base::BooleanHistogram::FactoryGet(name, base::Histogram::kNoFlags))
+
+// Support histograming of an enumerated value.  The samples should always be
+// strictly less than |boundary_value| -- this prevents you from running into
+// problems down the line if you add additional buckets to the histogram.  Note
+// also that, despite explicitly setting the minimum bucket value to |1| below,
+// it is fine for enumerated histograms to be 0-indexed -- this is because
+// enumerated histograms should never have underflow.
+#define LOCAL_HISTOGRAM_ENUMERATION(name, sample, boundary_value) \
+    STATIC_HISTOGRAM_POINTER_BLOCK(name, Add(sample), \
+        base::LinearHistogram::FactoryGet(name, 1, boundary_value, \
+            boundary_value + 1, base::HistogramBase::kNoFlags))
+
+// Support histograming of an enumerated value. Samples should be one of the
+// std::vector<int> list provided via |custom_ranges|. See comments above
+// CustomRanges::FactoryGet about the requirement of |custom_ranges|.
+// You can use the helper function CustomHistogram::ArrayToCustomRanges to
+// transform a C-style array of valid sample values to a std::vector<int>.
+#define LOCAL_HISTOGRAM_CUSTOM_ENUMERATION(name, sample, custom_ranges) \
+    STATIC_HISTOGRAM_POINTER_BLOCK(name, Add(sample), \
+        base::CustomHistogram::FactoryGet(name, custom_ranges, \
+                                          base::HistogramBase::kNoFlags))
+
+#define LOCAL_HISTOGRAM_MEMORY_KB(name, sample) LOCAL_HISTOGRAM_CUSTOM_COUNTS( \
+    name, sample, 1000, 500000, 50)
+
+//------------------------------------------------------------------------------
+// The following macros provide typical usage scenarios for callers that wish
+// to record histogram data, and have the data submitted/uploaded via UMA.
+// Not all systems support such UMA, but if they do, the following macros
+// should work with the service.
+
+#define UMA_HISTOGRAM_TIMES(name, sample) UMA_HISTOGRAM_CUSTOM_TIMES( \
+    name, sample, base::TimeDelta::FromMilliseconds(1), \
+    base::TimeDelta::FromSeconds(10), 50)
+
+#define UMA_HISTOGRAM_MEDIUM_TIMES(name, sample) UMA_HISTOGRAM_CUSTOM_TIMES( \
+    name, sample, base::TimeDelta::FromMilliseconds(10), \
+    base::TimeDelta::FromMinutes(3), 50)
+
+// Use this macro when times can routinely be much longer than 10 seconds.
+#define UMA_HISTOGRAM_LONG_TIMES(name, sample) UMA_HISTOGRAM_CUSTOM_TIMES( \
+    name, sample, base::TimeDelta::FromMilliseconds(1), \
+    base::TimeDelta::FromHours(1), 50)
+
+// Use this macro when times can routinely be much longer than 10 seconds and
+// you want 100 buckets.
+#define UMA_HISTOGRAM_LONG_TIMES_100(name, sample) UMA_HISTOGRAM_CUSTOM_TIMES( \
+    name, sample, base::TimeDelta::FromMilliseconds(1), \
+    base::TimeDelta::FromHours(1), 100)
+
+#define UMA_HISTOGRAM_CUSTOM_TIMES(name, sample, min, max, bucket_count) \
+    STATIC_HISTOGRAM_POINTER_BLOCK(name, AddTime(sample), \
+        base::Histogram::FactoryTimeGet(name, min, max, bucket_count, \
+            base::HistogramBase::kUmaTargetedHistogramFlag))
+
+#define UMA_HISTOGRAM_COUNTS(name, sample) UMA_HISTOGRAM_CUSTOM_COUNTS( \
+    name, sample, 1, 1000000, 50)
+
+#define UMA_HISTOGRAM_COUNTS_100(name, sample) UMA_HISTOGRAM_CUSTOM_COUNTS( \
+    name, sample, 1, 100, 50)
+
+#define UMA_HISTOGRAM_COUNTS_10000(name, sample) UMA_HISTOGRAM_CUSTOM_COUNTS( \
+    name, sample, 1, 10000, 50)
+
+#define UMA_HISTOGRAM_CUSTOM_COUNTS(name, sample, min, max, bucket_count) \
+    STATIC_HISTOGRAM_POINTER_BLOCK(name, Add(sample), \
+        base::Histogram::FactoryGet(name, min, max, bucket_count, \
+            base::HistogramBase::kUmaTargetedHistogramFlag))
+
+#define UMA_HISTOGRAM_MEMORY_KB(name, sample) UMA_HISTOGRAM_CUSTOM_COUNTS( \
+    name, sample, 1000, 500000, 50)
+
+#define UMA_HISTOGRAM_MEMORY_MB(name, sample) UMA_HISTOGRAM_CUSTOM_COUNTS( \
+    name, sample, 1, 1000, 50)
+
+#define UMA_HISTOGRAM_PERCENTAGE(name, under_one_hundred) \
+    UMA_HISTOGRAM_ENUMERATION(name, under_one_hundred, 101)
+
+#define UMA_HISTOGRAM_BOOLEAN(name, sample) \
+    STATIC_HISTOGRAM_POINTER_BLOCK(name, AddBoolean(sample), \
+        base::BooleanHistogram::FactoryGet(name, \
+            base::HistogramBase::kUmaTargetedHistogramFlag))
+
+// The samples should always be strictly less than |boundary_value|.  For more
+// details, see the comment for the |LOCAL_HISTOGRAM_ENUMERATION| macro, above.
+#define UMA_HISTOGRAM_ENUMERATION(name, sample, boundary_value) \
+    HISTOGRAM_ENUMERATION_WITH_FLAG(name, sample, boundary_value, \
+        base::HistogramBase::kUmaTargetedHistogramFlag)
+
+// Similar to UMA_HISTOGRAM_ENUMERATION, but used for recording stability
+// histograms.  Use this if recording a histogram that should be part of the
+// initial stability log.
+#define UMA_STABILITY_HISTOGRAM_ENUMERATION(name, sample, boundary_value) \
+    HISTOGRAM_ENUMERATION_WITH_FLAG(name, sample, boundary_value, \
+        base::HistogramBase::kUmaStabilityHistogramFlag)
+
+#define UMA_HISTOGRAM_CUSTOM_ENUMERATION(name, sample, custom_ranges) \
+    STATIC_HISTOGRAM_POINTER_BLOCK(name, Add(sample), \
+        base::CustomHistogram::FactoryGet(name, custom_ranges, \
+            base::HistogramBase::kUmaTargetedHistogramFlag))
+
+#endif  // BASE_METRICS_HISTOGRAM_MACROS_H_