Remove unused synthesizedClasses field from DexApplication.Builder

Change-Id: I49ae3321b23f4dbee83c51504a1b94c1bdaf513e
diff --git a/src/main/java/com/android/tools/r8/graph/DexApplication.java b/src/main/java/com/android/tools/r8/graph/DexApplication.java
index 0d83712..bed4416 100644
--- a/src/main/java/com/android/tools/r8/graph/DexApplication.java
+++ b/src/main/java/com/android/tools/r8/graph/DexApplication.java
@@ -173,13 +173,10 @@
     final Timing timing;
     DexApplicationReadFlags flags;
 
-    private final Collection<DexProgramClass> synthesizedClasses;
-
     public Builder(InternalOptions options, Timing timing) {
       this.options = options;
       this.dexItemFactory = options.itemFactory;
       this.timing = timing;
-      this.synthesizedClasses = new ArrayList<>();
     }
 
     abstract T self();
@@ -192,7 +189,6 @@
       timing = application.timing;
       options = application.options;
       dexItemFactory = application.dexItemFactory;
-      synthesizedClasses = new ArrayList<>();
     }
 
     public boolean isDirect() {
@@ -261,21 +257,10 @@
       return self();
     }
 
-    public synchronized T addSynthesizedClass(DexProgramClass synthesizedClass) {
-      assert synthesizedClass.isProgramClass() : "All synthesized classes must be program classes";
-      addProgramClass(synthesizedClass);
-      synthesizedClasses.add(synthesizedClass);
-      return self();
-    }
-
     public List<DexProgramClass> getProgramClasses() {
       return programClasses;
     }
 
-    public Collection<DexProgramClass> getSynthesizedClasses() {
-      return synthesizedClasses;
-    }
-
     public abstract DexApplication build();
   }