Add todo for possible valid frames of different length.

Bug: b/229826687
Change-Id: I6402493b64bbf28c476a340c6252a0c8765135ca
diff --git a/src/main/java/com/android/tools/r8/cf/code/CfFrameVerificationHelper.java b/src/main/java/com/android/tools/r8/cf/code/CfFrameVerificationHelper.java
index c81abe4..a3fc4d1 100644
--- a/src/main/java/com/android/tools/r8/cf/code/CfFrameVerificationHelper.java
+++ b/src/main/java/com/android/tools/r8/cf/code/CfFrameVerificationHelper.java
@@ -326,6 +326,7 @@
       Int2ReferenceSortedMap<FrameType> destLocals,
       DexItemFactory factory,
       BiPredicate<DexType, DexType> isJavaAssignable) {
+    // TODO(b/229826687): The tail of locals could have top(s) at destination but still be valid.
     final int localsLastKey = sourceLocals.isEmpty() ? -1 : sourceLocals.lastIntKey();
     final int otherLocalsLastKey = destLocals.isEmpty() ? -1 : destLocals.lastIntKey();
     if (localsLastKey < otherLocalsLastKey) {