Cleanup histograms from message loop, as well as kHexRangePrintingFlag.

base/metrics/histogram_base.h

Index: base/metrics/histogram_base.h
diff --git a/base/metrics/histogram_base.h b/base/metrics/histogram_base.h
index c699b68ba1bb7c2bbe518f3a80b759d53054dad3..9f836073de14062a5a42896310c4215115d424f1 100644
--- a/base/metrics/histogram_base.h
+++ b/base/metrics/histogram_base.h
@@ -121,11 +121,6 @@ class BASE_EXPORT HistogramBase {
     // MemoryAllocator, and that loaded into the Histogram module before this
     // histogram is created.
     kIsPersistent = 0x40,
-
-    // TODO(rkaplow): Look into this, but looks like this is unused and can
-    // be removed.
-    // Only for Histogram and its sub classes: fancy bucket-naming support.
-    kHexRangePrintingFlag = 0x8000,
   };
 
   // Histogram data inconsistency types.