Reland "Enable interface merging in second round of class merging"

This reverts commit 1188c195bc5fb277e7cd59572c674bb06ba23f6a.

Change-Id: Ia47dba6af52493305bb287e33bd20f069f045369
diff --git a/src/test/examples/classmerging/SimpleInterfaceAccessTest.java b/src/test/examples/classmerging/SimpleInterfaceAccessTest.java
index 6fde90e..804b4ed 100644
--- a/src/test/examples/classmerging/SimpleInterfaceAccessTest.java
+++ b/src/test/examples/classmerging/SimpleInterfaceAccessTest.java
@@ -32,12 +32,14 @@
   }
 
   // Should only be merged into OtherSimpleInterfaceImpl if access modifications are allowed.
+  @NoHorizontalClassMerging
   public interface SimpleInterface {
 
     void foo();
   }
 
   // Should only be merged into OtherSimpleInterfaceImpl if access modifications are allowed.
+  @NoHorizontalClassMerging
   public interface OtherSimpleInterface {
 
     void bar();