Moved scoped_histogram_timer to the main histogram_macros.h.

base/metrics/histogram_macros.h

 // 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"
@@ skipping 211 matching lines @@
 // 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))
 
+// Scoped class which logs its time on this earth as a UMA statistic.  Must be
+// a #define macro since UMA macros prevent variables as names.  The nested
+// macro is necessary to expand __COUNTER__ to an actual value.
+#define SCOPED_UMA_HISTOGRAM_TIMER(name) \
+  SCOPED_UMA_HISTOGRAM_TIMER_EXPANDER(name, __COUNTER__)
+
+#define SCOPED_UMA_HISTOGRAM_TIMER_EXPANDER(name, key) \
+  SCOPED_UMA_HISTOGRAM_TIMER_UNIQUE(name, key)
+
+#define SCOPED_UMA_HISTOGRAM_TIMER_UNIQUE(name, key) \
+  class ScopedHistogramTimer##key { \
+   public: \
+    ScopedHistogramTimer##key() : constructed_(base::TimeTicks::Now()) {} \
+    ~ScopedHistogramTimer##key() { \
+      base::TimeDelta elapsed = base::TimeTicks::Now() - constructed_; \
+      UMA_HISTOGRAM_TIMES(name, elapsed); \
+    } \
+   private: \
+    base::TimeTicks constructed_; \
+  } scoped_histogram_timer_##key
+
 #endif  // BASE_METRICS_HISTOGRAM_MACROS_H_