Support using UMA_HISTOGRAM_CUSTOM_ENUMERATION from the renderer.

base/metrics/histogram.h

Index: base/metrics/histogram.h
diff --git a/base/metrics/histogram.h b/base/metrics/histogram.h
index e5f0d046725b2547a600e7925f1843c91ce34c25..a0751b26e7ae22e63636a595ad0f9d9dc468c90a 100644
--- a/base/metrics/histogram.h
+++ b/base/metrics/histogram.h
@@ -855,6 +855,9 @@ class BASE_EXPORT CachedRanges {
   // Return true iff |other| object has same ranges_ as |this| object's ranges_.
   bool Equals(CachedRanges* other) const;
 
+  bool Serialize(Pickle* pickle) const;
+  bool Deserialize(void** iter, const Pickle& pickle);
+
  private:
   // Allow tests to corrupt our innards for testing purposes.
   FRIEND_TEST(HistogramTest, CorruptBucketBounds);