Update CHANGES.txt for commit of HADOOP-12107 to branch-2.7 and branch-2.6

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -1649,6 +1649,9 @@ Release 2.7.3 - UNRELEASED
     HADOOP-12588. Fix intermittent test failure of TestGangliaMetrics.
     (Masatake Iwasaki via aajisaka)
 
+    HADOOP-12107. long running apps may have a huge number of StatisticsData
+    instances under FileSystem (Sangjin Lee via Ming Ma)
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES
@@ -2443,6 +2446,9 @@ Release 2.6.4 - UNRELEASED
     HADOOP-11252. RPC client does not time out by default.
     (Wilfred Spiegelenburg and Masatake Iwasaki via aajisaka)
 
+    HADOOP-12107. long running apps may have a huge number of StatisticsData
+    instances under FileSystem (Sangjin Lee via Ming Ma)
+
 Release 2.6.3 - 2015-12-17
 
   INCOMPATIBLE CHANGES