Update 2.15.9 release notes

Change-Id: I52f2de3bb5c838c731115272fbd3ae6008df0929
diff --git a/pages/site/releases/2.15.md b/pages/site/releases/2.15.md
index a452b8c..9d38bad 100644
--- a/pages/site/releases/2.15.md
+++ b/pages/site/releases/2.15.md
@@ -401,6 +401,9 @@
 
 ### 2.15.9
 
+* [Issue 10326](https://bugs.chromium.org/p/gerrit/issues/detail?id=10326):
+Fix excessive heap usage when listing projects.
+
 * [Issue 10021](https://bugs.chromium.org/p/gerrit/issues/detail?id=10021):
 Encode and quote project name in download commands.
 
@@ -424,6 +427,8 @@
   The new method allows to set the base revision, and request to include the
   files and download commands.
 
+* Add method to set a file's "reviewed" flag on the File API.
+
 * Fix internal server error when getting commit info for root commit.
 
 * Add `--skip-project` option to the `MigrateToNoteDb` command.
@@ -431,9 +436,18 @@
   This is useful when only a few projects should be skipped but all others
   should be migrated.
 
-* [Issue 7669](https://bugs.chromium.org/p/gerrit/issues/detail?id=7669),
-[Issue 9614](https://bugs.chromium.org/p/gerrit/issues/detail?id=9614):
-Polygerrit: Fix '/' getting typed in search bar when pressed.
+* Polygerrit fixes
+
+  * [Issue 7669](https://bugs.chromium.org/p/gerrit/issues/detail?id=7669),
+  [Issue 9614](https://bugs.chromium.org/p/gerrit/issues/detail?id=9614):
+  Fix '/' getting typed in the search bar when pressed.
+
+  * [Issue 10151](https://bugs.chromium.org/p/gerrit/issues/detail?id=10151):
+  Fix support for deleting branches.
+
+  * [Issue 10019](https://bugs.chromium.org/p/gerrit/issues/detail?id=10019):
+  Fix deletion of branch that `HEAD` pointed to after `HEAD` was moved to a
+  different branch.
 
 ### 2.15.8