Update to perflib-25.0.0 to improve processing performance.

Bug: 24542836
Change-Id: I800dedd50c535df99a5cc38cd9da32fc33a35997
diff --git a/tools/ahat/README.txt b/tools/ahat/README.txt
index d9b26bc..0cd77ab 100644
--- a/tools/ahat/README.txt
+++ b/tools/ahat/README.txt
@@ -77,7 +77,12 @@
  * Instance.isRoot and Instance.getRootTypes.
 
 Release History:
- 0.4 Pending
+ 0.6 Pending
+
+ 0.5 Apr 19, 2016
+   Update perflib to perflib-25.0.0 to improve processing performance.
+
+ 0.4 Feb 23, 2016
    Annotate char[] objects with their string values.
    Show registered native allocations for heap dumps that support it.