Simple iterator for textblobs

bug: skia:9503

Change-Id: I5b4e2434c6085d048d6d0fc42b2b928439b1066b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/246296
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
diff --git a/RELEASE_NOTES.txt b/RELEASE_NOTES.txt
index 73e2ba5..0921288 100644
--- a/RELEASE_NOTES.txt
+++ b/RELEASE_NOTES.txt
@@ -4,6 +4,9 @@
 
 * * *
 
+  * SkTextBlob::Iter to discover the glyph indices and typefaces in each run
+    https://skia-review.googlesource.com/246296
+
 Milestone 79
 
 [Insert new notes here.]