profiling: Link design doc in README.

Change-Id: I225fba17b95231b73d8b52c31ef2ce6da01b940e
diff --git a/src/profiling/memory/README.md b/src/profiling/memory/README.md
index 619dba8..01a2641 100644
--- a/src/profiling/memory/README.md
+++ b/src/profiling/memory/README.md
@@ -4,6 +4,7 @@
 subject to frequent change and will be obsoleted once heapprofd is integrated
 into Perfetto._
 
+Googlers, for design doc see: http://go/heapprofd-design
 
 ## Using convenience script