Add UMA histograms to track very brief or frequent tabs and JS dialogs.

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 72f7d86167a58ece3497f86c8c9d0eec73475650..92cd34e1cc7805afddfc451ba25d75b8169f288b 100644
--- a/base/metrics/histogram_macros.h
+++ b/base/metrics/histogram_macros.h
@@ -182,6 +182,12 @@
     name, sample, base::TimeDelta::FromMilliseconds(1), \
     base::TimeDelta::FromHours(1), 100)
 
+// Use this macro to capture fine-grained timing variations from under a
+// millisecond up to a minute, using 100 buckets.
+#define UMA_HISTOGRAM_FINE_TIMES_100(name, sample) UMA_HISTOGRAM_CUSTOM_TIMES( \
+    name, sample, base::TimeDelta::FromMicroseconds(100), \
+    base::TimeDelta::FromMinutes(1), 100)
+
 #define UMA_HISTOGRAM_CUSTOM_TIMES(name, sample, min, max, bucket_count) \
     STATIC_HISTOGRAM_POINTER_BLOCK(name, AddTime(sample), \
         base::Histogram::FactoryTimeGet(name, min, max, bucket_count, \