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diff --git a/net/disk_cache/histogram_macros.h b/net/disk_cache/histogram_macros.h
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+// Copyright (c) 2009 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.
+
+// This file contains macros to simplify histogram reporting from the disk
+// cache. The main issue is that we want to have separate histograms for each
+// type of cache (regular vs. media, etc), without adding the complexity of
+// keeping track of a potentially large number of histogram objects that have to
+// survive the backend object that created them.
+
+#ifndef NET_DISK_CACHE_HISTOGRAM_MACROS_H_
+#define NET_DISK_CACHE_HISTOGRAM_MACROS_H_
+
+// HISTOGRAM_HOURS will collect time related data with a granularity of hours
+// and normal values of a few months.
+#define UMA_HISTOGRAM_HOURS UMA_HISTOGRAM_COUNTS_10000
+
+// HISTOGRAM_AGE will collect time elapsed since |initial_time|, with a
+// granularity of hours and normal values of a few months.
+#define UMA_HISTOGRAM_AGE(name, initial_time)\
+    UMA_HISTOGRAM_COUNTS_10000(name, (Time::Now() - initial_time).InHours())
+
+// HISTOGRAM_AGE_MS will collect time elapsed since |initial_time|, with the
+// normal resolution of the UMA_HISTOGRAM_TIMES.
+#define UMA_HISTOGRAM_AGE_MS(name, initial_time)\
+    UMA_HISTOGRAM_TIMES(name, Time::Now() - initial_time)
+
+#define UMA_HISTOGRAM_CACHE_ERROR(name, sample) do { \
+    static LinearHistogram counter((name), 0, 49, 50); \
+    counter.SetFlags(kUmaTargetedHistogramFlag); \
+    counter.Add(sample); \
+  } while (0)
+
+#ifdef NET_DISK_CACHE_BACKEND_IMPL_CC_
+#define BACKEND_OBJ this
+#else
+#define BACKEND_OBJ backend_
+#endif
+
+// Generates a UMA histogram of the given type, generating the proper name for
+// it (asking backend_->HistogramName), and adding the provided sample.
+// For example, to generate a regualar UMA_HISTOGRAM_COUNTS, this macro would
+// be used as:
+//  CACHE_UMA(COUNTS, "MyName", 0, 20);
+//  CACHE_UMA(COUNTS, "MyExperiment", 530, 55);
+// which roughly translates to:
+//  UMA_HISTOGRAM_COUNTS("DiskCache.2.MyName", 20);  // "2" is the CacheType.
+//  UMA_HISTOGRAM_COUNTS("DiskCache.2.MyExperiment_530", 55);
+//
+#define CACHE_UMA(type, name, experiment, sample) {\
+    const std::string my_name = BACKEND_OBJ->HistogramName(name, experiment);\
+    switch (BACKEND_OBJ->cache_type()) {\
+      case net::DISK_CACHE:\
+        UMA_HISTOGRAM_##type(my_name.data(), sample);\
+        break;\
+      case net::MEDIA_CACHE:\
+        UMA_HISTOGRAM_##type(my_name.data(), sample);\
+        break;\
+      case net::TEMP_MEDIA_CACHE:\
+        UMA_HISTOGRAM_##type(my_name.data(), sample);\
+        break;\
+      default:\
+        NOTREACHED();\
+        break;\
+    }\
+  }
+
+#endif  // NET_DISK_CACHE_HISTOGRAM_MACROS_H_