ART: Add clarifying comment

Change-Id: I189ec4cae0aa1a5245a79e86d1ec0592e38eac4a
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index de3f266..a0cfe8e 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -1686,6 +1686,8 @@
     // (2) the reverse post order of that graph,
     // (3) the potential loop information they are now in,
     // (4) try block membership.
+    // Note that we do not need to update catch phis because catch blocks cannot
+    // reference vregs from the inlined method.
 
     // We don't add the entry block, the exit block, and the first block, which
     // has been merged with `at`.