Upstream Chrome on iOS source code [5/11].

ios/chrome/browser/ui/first_run/first_run_histograms.h

+// Copyright 2016 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 IOS_CHROME_BROWSER_UI_FIRST_RUN_FIRST_RUN_HISTOGRAMS_H_
+#define IOS_CHROME_BROWSER_UI_FIRST_RUN_FIRST_RUN_HISTOGRAMS_H_
+
+#include "base/metrics/histogram.h"
+
+// HISTOGRAM_POINTER_BLOCK differ from STATIC_HISTOGRAM_POINTER_BLOCK
+// on using static histogram pointer, in this one we create a new histogram
+// from the histogram_factory_get_invocation each time this is called.
+// This is needed on the first run because the same funciton try to log
+// different histogram names, also we don't need static histogram as first run
+// logging only happens once (may be little more in some cases).
+#define HISTOGRAM_POINTER_BLOCK(constant_histogram_name,                       \
+                                histogram_add_method_invocation,               \
+                                histogram_factory_get_invocation)              \
+  do {                                                                         \
+    base::HistogramBase* histogram_pointer = histogram_factory_get_invocation; \
+    histogram_pointer->histogram_add_method_invocation;                        \
+  } while (0)
+
+// This UMA_HISTOGRAM_CUSTOM_TIMES_FIRST_RUN uses the HISTOGRAM_POINTER_BLOCK
+// instead of STATIC_HISTOGRAM_POINTER_BLOCK which handles being called with
+// different names from same function.
+#define UMA_HISTOGRAM_CUSTOM_TIMES_FIRST_RUN(name, sample, min, max, \
+                                             bucket_count)           \
+  HISTOGRAM_POINTER_BLOCK(name, AddTime(sample),                     \
+                          base::Histogram::FactoryTimeGet(           \
+                              name, min, max, bucket_count,          \
+                              base::HistogramBase::kUmaTargetedHistogramFlag))
+
+#endif  // IOS_CHROME_BROWSER_UI_FIRST_RUN_FIRST_RUN_HISTOGRAMS_H_