Add histogram for native allocations

Shows up in traces.txt, sample output:
Histogram of native allocation 0:4315,131072:33,1179648:3 bucket size 131072
Histogram of native free 0:995,131072:19,1179648:2 bucket size 131072

Bug: 28680116

(cherry picked from commit 0dce75dc6945c221a054eb9c479fb60efd193719)

Change-Id: Iaa07c6b8da0d6bab64a8fd4af8a02fc0b8c70e9e

1 files changed, 4 insertions, 0 deletions

diff --git a/runtime/base/histogram.h b/runtime/base/histogram.h
index bcb7b3b769..0e3bc8e1b4 100644
--- a/runtime/base/histogram.h
+++ b/runtime/base/histogram.h
@@ -85,6 +85,10 @@ template <class Value> class Histogram {
     return max_value_added_;
   }
 
+  Value BucketWidth() const {
+    return bucket_width_;
+  }
+
   const std::string& Name() const {
     return name_;
   }