Add helper macros for calling a histogram with different names.

webrtc/system_wrappers/include/metrics.h

 //
 // Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 //
 // Use of this source code is governed by a BSD-style license
 // that can be found in the LICENSE file in the root of the source
 // tree. An additional intellectual property rights grant can be found
 // in the file PATENTS.  All contributing project authors may
 // be found in the AUTHORS file in the root of the source tree.
 //
 
@@ skipping 135 matching lines @@
 
 // Deprecated.
 // The histogram is constructed/found for each call.
 // May be used for histograms with infrequent updates.
 #define RTC_HISTOGRAM_COMMON_BLOCK_SLOW(name, sample, factory_get_invocation) \
   do { \
     webrtc::metrics::Histogram* histogram_pointer = factory_get_invocation; \
     webrtc::metrics::HistogramAdd(histogram_pointer, name, sample); \
   } while (0)
 
+
+// Helper macros.
+// Macros for calling a histogram with varying name (e.g. when using a metric
+// in different modes such as real-time vs screenshare).
+#define RTC_HISTOGRAMS_COUNTS_100(index, name, sample) \
+  RTC_HISTOGRAMS_COMMON(index, name, sample, \
+      RTC_HISTOGRAM_COUNTS(name, sample, 1, 100, 50))
+
+#define RTC_HISTOGRAMS_COUNTS_200(index, name, sample) \
+  RTC_HISTOGRAMS_COMMON(index, name, sample, \
+      RTC_HISTOGRAM_COUNTS(name, sample, 1, 200, 50))
+
+#define RTC_HISTOGRAMS_COUNTS_1000(index, name, sample) \
+  RTC_HISTOGRAMS_COMMON(index, name, sample, \
+      RTC_HISTOGRAM_COUNTS(name, sample, 1, 1000, 50))
+
+#define RTC_HISTOGRAMS_COUNTS_10000(index, name, sample) \
+  RTC_HISTOGRAMS_COMMON(index, name, sample, \
+      RTC_HISTOGRAM_COUNTS(name, sample, 1, 10000, 50))
+
+#define RTC_HISTOGRAMS_COUNTS_100000(index, name, sample) \
+  RTC_HISTOGRAMS_COMMON(index, name, sample, \
+      RTC_HISTOGRAM_COUNTS(name, sample, 1, 100000, 50))
+
+#define RTC_HISTOGRAMS_ENUMERATION(index, name, sample, boundary) \
+  RTC_HISTOGRAMS_COMMON(index, name, sample, \
+      RTC_HISTOGRAM_ENUMERATION(name, sample, boundary))
+
+#define RTC_HISTOGRAMS_PERCENTAGE(index, name, sample) \
+  RTC_HISTOGRAMS_COMMON(index, name, sample, \
+      RTC_HISTOGRAM_PERCENTAGE(name, sample))
+
+#define RTC_HISTOGRAMS_COMMON(index, name, sample, macro_invocation) \
+  do { \
+    RTC_DCHECK_GE(index, 0); \

[pbos-webrtc, 2016/01/19 14:13:35]

RTC_DCHECK(index >= 0) so you can use both size_t and int here (I think).

[åsapersson, 2016/01/20 10:50:52]

Done.

+    RTC_DCHECK_LE(index, 2); \
+    switch (index) { \
+      case 0: \
+        macro_invocation; \
+        break; \
+      case 1: \
+        macro_invocation; \
+        break; \
+      case 2: \
+        macro_invocation; \
+        break; \
+      default: \
+        RTC_NOTREACHED(); \
+    } \
+  } while (0)
+
+
 namespace webrtc {
 namespace metrics {
 
 // Time that should have elapsed for stats that are gathered once per call.
 enum { kMinRunTimeInSeconds = 10 };
 
 class Histogram;
 
 // Functions for getting pointer to histogram (constructs or finds the named
 // histogram).
@@ skipping 10 matching lines @@
 // Function for adding a |sample| to a histogram.
 // |name| can be used to verify that it matches the histogram name.
 void HistogramAdd(
     Histogram* histogram_pointer, const std::string& name, int sample);
 
 }  // namespace metrics
 }  // namespace webrtc
 
 #endif  // WEBRTC_SYSTEM_WRAPPERS_INCLUDE_METRICS_H_