AAPT2: Add Manifest fixing/validation

Change-Id: I7f6d8b74d1c590adc356b4da55cb6cb777cdf1da
diff --git a/tools/aapt2/ResourceUtils.h b/tools/aapt2/ResourceUtils.h
index 118a2ee..3c532de 100644
--- a/tools/aapt2/ResourceUtils.h
+++ b/tools/aapt2/ResourceUtils.h
@@ -49,6 +49,11 @@
                        bool* outCreate = nullptr, bool* outPrivate = nullptr);
 
 /*
+ * Returns true if the string is in the form of a resource reference (@[+][package:]type/name).
+ */
+bool isReference(const StringPiece16& str);
+
+/*
  * Returns true if the string was parsed as an attribute reference (?[package:]type/name),
  * with `outReference` set to the parsed reference.
  */