Make control reducer revisit newly introduced merges.

test/mjsunit/compiler/regress-445876.js

Index: test/mjsunit/compiler/regress-445876.js
diff --git a/test/mjsunit/compiler/regress-ntl-effect.js b/test/mjsunit/compiler/regress-445876.js
similarity index 66%
copy from test/mjsunit/compiler/regress-ntl-effect.js
copy to test/mjsunit/compiler/regress-445876.js
index 708fe32828c9197dfa3d8c371ab01cbc1ad3317a..30e10e56c3ac424fb8843b700bec2af5ded334ac 100644
--- a/test/mjsunit/compiler/regress-ntl-effect.js
+++ b/test/mjsunit/compiler/regress-445876.js
@@ -4,13 +4,9 @@
 
 // Flags: --allow-natives-syntax
 
-function g() {
-  throw 0;
+function f(x) {
+  while (1) { s++; }
+  while (x) { s++; }
 }
 
-function f() {
-  g();
-  while (1) {}
-}
-
-assertThrows(function () { f(); });
+assertThrows(function () { f(1); });