import debug/gosym from usr/austin/sym

R=austin
DELTA=958  (956 added, 0 deleted, 2 changed)
OCL=34180
CL=34212
diff --git a/src/pkg/io/io.go b/src/pkg/io/io.go
index 5462038..be6614b 100644
--- a/src/pkg/io/io.go
+++ b/src/pkg/io/io.go
@@ -321,3 +321,7 @@
 	return s.r.ReadAt(p, off);
 }
 
+// Size returns the size of the section in bytes.
+func (s *SectionReader) Size() int64 {
+	return s.limit - s.base
+}