Add a basic exact linear macro. Ends up being the same as enum, but making it explicit will make ou…

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
index 9cb21ec563a2ed54e45cdd885b4d2501a84ad985..fe984bbad02cc79e729969d840768e8d94fbb18c 100644
--- a/base/metrics/histogram_macros.h
+++ b/base/metrics/histogram_macros.h
@@ -53,17 +53,26 @@
             base::HistogramBase::kUmaTargetedHistogramFlag))
 
 //------------------------------------------------------------------------------
-// Percentage histograms.
+// Linear histograms.
 
 // All of these macros must be called with |name| as a runtime constant.
 
+// Used for capturing integer data with a linear bucketing scheme. This can be
+// used when you want the exact value of some small numeric count, with a max of
+// 100 or less. If you need to capture a range of greater than 100, we recommend
+// the use of the COUNT histograms below.
+
+// Sample usage:
+//   UMA_HISTOGRAM_EXACT_LINEAR("Histogram.Linear", count, 10);
+#define UMA_HISTOGRAM_EXACT_LINEAR(name, sample, value_max)                    \
+    UMA_HISTOGRAM_ENUMERATION(name, sample, value_max+1)
+
 // Used for capturing basic percentages. This will be 100 buckets of size 1.
 
 // Sample usage:
 //   UMA_HISTOGRAM_PERCENTAGE("Histogram.Percent", percent_as_int);
-#define UMA_HISTOGRAM_PERCENTAGE(name, under_one_hundred)                      \
-    UMA_HISTOGRAM_ENUMERATION(name, under_one_hundred, 101)
-
+#define UMA_HISTOGRAM_PERCENTAGE(name, percent_as_int)                         \
+    UMA_HISTOGRAM_ENUMERATION(name, percent_as_int, 101)
 
 //------------------------------------------------------------------------------
 // Count histograms. These are used for collecting numeric data. Note that we
@@ -117,7 +126,6 @@
         name, sample, min, max, bucket_count,                                  \
         base::HistogramBase::kUmaTargetedHistogramFlag)
 
-
 //------------------------------------------------------------------------------
 // Timing histograms. These are used for collecting timing data (generally
 // latencies).