[turbofan] Improve typed lowering for JSToBoolean.

src/compiler/access-builder.cc

Index: src/compiler/access-builder.cc
diff --git a/src/compiler/access-builder.cc b/src/compiler/access-builder.cc
index 051b47c13ae23474832d9840979c373d5f4e8f1c..2c270220df88fdac27c95dd00f9868a0d4d2b0de 100644
--- a/src/compiler/access-builder.cc
+++ b/src/compiler/access-builder.cc
@@ -59,6 +59,13 @@ FieldAccess AccessBuilder::ForMapInstanceType() {
 
 
 // static
+FieldAccess AccessBuilder::ForStringLength() {
+  return {kTaggedBase, String::kLengthOffset, Handle<Name>(),
+          Type::SignedSmall(), kMachAnyTagged};
+}
+
+
+// static
 FieldAccess AccessBuilder::ForValue() {
   return {kTaggedBase, JSValue::kValueOffset, Handle<Name>(), Type::Any(),
           kMachAnyTagged};