Reuse cached DexMethod for requireNonNull

Change-Id: I451cf2486642892371e42a3cbb29117e473bb1fe
diff --git a/src/main/java/com/android/tools/r8/ir/desugar/BackportedMethodRewriter.java b/src/main/java/com/android/tools/r8/ir/desugar/BackportedMethodRewriter.java
index 86417a1..ba3615c 100644
--- a/src/main/java/com/android/tools/r8/ir/desugar/BackportedMethodRewriter.java
+++ b/src/main/java/com/android/tools/r8/ir/desugar/BackportedMethodRewriter.java
@@ -345,9 +345,7 @@
       addProvider(new MethodGenerator(method, BackportedMethods::ObjectsMethods_hashCode));
 
       // T Objects.requireNonNull(T obj)
-      name = factory.createString("requireNonNull");
-      proto = factory.createProto(factory.objectType, factory.objectType);
-      method = factory.createMethod(type, proto, name);
+      method = factory.objectsMethods.requireNonNull;
       addProvider(new InvokeRewriter(method, ObjectsMethodRewrites::rewriteRequireNonNull));
 
       // T Objects.requireNonNull(T obj, String message)