Add a dexItemFactory getter to AppView

This CL also fixes a NPE that arises from the call super(null, null) in AppViewWithLiveness to the AppView constructor.

Change-Id: I948d812b1cb39e78c9cc2e57e591305798f4d985

src/main/java/com/android/tools/r8/graph/AppView.java

diff --git a/src/main/java/com/android/tools/r8/graph/AppView.java b/src/main/java/com/android/tools/r8/graph/AppView.java
index 8e468a1..64a4ce4 100644
--- a/src/main/java/com/android/tools/r8/graph/AppView.java
+++ b/src/main/java/com/android/tools/r8/graph/AppView.java
@@ -14,7 +14,7 @@
 
   public AppView(T appInfo, GraphLense graphLense) {
     this.appInfo = appInfo;
-    this.dexItemFactory = appInfo.dexItemFactory;
+    this.dexItemFactory = appInfo != null ? appInfo.dexItemFactory : null;
     this.graphLense = graphLense;
   }
 
@@ -61,6 +61,11 @@
     }
 
     @Override
+    public DexItemFactory getDexItemFactory() {
+      return AppView.this.dexItemFactory;
+    }
+
+    @Override
     public GraphLense getGraphLense() {
       return AppView.this.getGraphLense();
     }