Use filter context to track stats better in SDCH filtering

base/histogram.h

Index: base/histogram.h
===================================================================
--- base/histogram.h	(revision 11636)
+++ base/histogram.h	(working copy)
@@ -60,6 +60,11 @@
     counter.Add(sample); \
   } while (0)
 
+#define HISTOGRAM_PERCENTAGE(name, under_one_hundred) do { \
+    static LinearHistogram counter((name), 1, 100, 101); \
+    counter.Add(under_one_hundred); \
+  } while (0)
+
 // For folks that need real specific times, use this, but you'll only get
 // samples that are in the range (overly large samples are discarded).
 #define HISTOGRAM_CLIPPED_TIMES(name, sample, min, max, bucket_count) do { \
@@ -98,6 +103,8 @@
 #define DHISTOGRAM_COUNTS(name, sample) HISTOGRAM_COUNTS(name, sample)
 #define DASSET_HISTOGRAM_COUNTS(name, sample) ASSET_HISTOGRAM_COUNTS(name, \
                                                                      sample)
+#define DHISTOGRAM_PERCENTAGE(name, under_one_hundred) HISTOGRAM_PERCENTAGE(\
+    name, under_one_hundred)
 #define DHISTOGRAM_CLIPPED_TIMES(name, sample, min, max, bucket_count) \
     HISTOGRAM_CLIPPED_TIMES(name, sample, min, max, bucket_count)
 
@@ -106,6 +113,7 @@
 #define DHISTOGRAM_TIMES(name, sample) do {} while (0)
 #define DHISTOGRAM_COUNTS(name, sample) do {} while (0)
 #define DASSET_HISTOGRAM_COUNTS(name, sample) do {} while (0)
+#define DHISTOGRAM_PERCENTAGE(name, under_one_hundred) do {} while (0)
 #define DHISTOGRAM_CLIPPED_TIMES(name, sample, min, max, bucket_count) \
     do {} while (0)
 
@@ -176,6 +184,12 @@
     counter.Add(sample); \
   } while (0)
 
+#define UMA_HISTOGRAM_PERCENTAGE(name, under_one_hundred) do { \
+    static LinearHistogram counter((name), 1, 100, 101); \
+    counter.SetFlags(kUmaTargetedHistogramFlag); \
+    counter.Add(under_one_hundred); \
+  } while (0)
+
 //------------------------------------------------------------------------------
 
 class Histogram : public StatsRate {