Fix memory corruption bug in impl/memory

impl/memory/doc.go

Index: impl/memory/doc.go
diff --git a/impl/memory/doc.go b/impl/memory/doc.go
index 0954f1aff3b8ef180b10224a2723ebe321cd4ee8..ef89fe1924d96e82c35f12d36c8bbef671988f85 100644
--- a/impl/memory/doc.go
+++ b/impl/memory/doc.go
@@ -5,4 +5,14 @@
 // Package memory provides an implementation of infra/gae/libs/wrapper which
 // backs to local memory ONLY. This is useful for unittesting, and is also used
 // for the nested-transaction filter implementation.
+//
+// Debug EnvVars
+//
+// To debug GKVLite memory access for a binary that uses this memory
+// implementation, you may set the flag:
+//   -luci.gae.gkvlite_trace_folder
+// to `/path/to/some/folder`. Every gkvlite memory store will be assigned
+// a numbered file in that folder, and all access to that store will be logged
+// to that file. Setting this to "-" will cause the trace information to dump to
+// stdout.
 package memory