AAPT2: Add library support

Change-Id: I307f56d9631784ab29ee4156d94886f9b2f25b30
diff --git a/tools/aapt2/StringPool.h b/tools/aapt2/StringPool.h
index 2aa5b65..64772a4 100644
--- a/tools/aapt2/StringPool.h
+++ b/tools/aapt2/StringPool.h
@@ -158,6 +158,12 @@
     StyleRef makeRef(const StyleString& str, const Context& context);
 
     /**
+     * Adds a style from another string pool. Returns a reference to the
+     * style in the string pool.
+     */
+    StyleRef makeRef(const StyleRef& ref);
+
+    /**
      * Moves pool into this one without coalescing strings. When this
      * function returns, pool will be empty.
      */