[turbofan] Respect effect input when lowering JSToBoolean for string inputs.

test/mjsunit/regress/regress-4493-1.js

Index: test/mjsunit/regress/regress-4493-1.js
diff --git a/test/mjsunit/compiler/regress-491578.js b/test/mjsunit/regress/regress-4493-1.js
similarity index 59%
copy from test/mjsunit/compiler/regress-491578.js
copy to test/mjsunit/regress/regress-4493-1.js
index c27570456c31e9a191fe1f4f1ea17b80f29de98e..a24c8b07dceebed510e67dcbb24b8b8206c8f949 100644
--- a/test/mjsunit/compiler/regress-491578.js
+++ b/test/mjsunit/regress/regress-4493-1.js
@@ -4,12 +4,13 @@
 
 // Flags: --allow-natives-syntax
 
-function foo(x) {
-  if (x === undefined) return;
-  while (true) {
-    while (1 || 2) { }
-    f();
-  }
-}
+function baz(x, f) { return x.length; };
+
+function bar(x, y) {
+  if (y) {}
+  baz(x, function() { return x; });
+};
+
+function foo(x) { bar(x, ''); }
 %OptimizeFunctionOnNextCall(foo);
-foo();
+foo(['a']);