Override asArray on ArrayReference

Otherwise, the method as no use at all.

Change-Id: I24a2f4ad9aadccfcdb2e0583316124a5d147233b

src/main/java/com/android/tools/r8/references/ArrayReference.java

diff --git a/src/main/java/com/android/tools/r8/references/ArrayReference.java b/src/main/java/com/android/tools/r8/references/ArrayReference.java
index f95a60c..7946c2f 100644
--- a/src/main/java/com/android/tools/r8/references/ArrayReference.java
+++ b/src/main/java/com/android/tools/r8/references/ArrayReference.java
@@ -60,6 +60,11 @@
   }
 
   @Override
+  public ArrayReference asArray() {
+    return this;
+  }
+
+  @Override
   public String getDescriptor() {
     return descriptor;
   }