AAPT2: Fixup namespace implementation

A few pieces were missing in the namespace mangling implementation.
Namespace aware libraries now work, along with R class generation.

Bug: 64706588
Test: make AaptTestNamespace_App
Change-Id: I12f78d6aa909e782c0faf7ceaa36058f2e6c864a
diff --git a/tools/aapt2/xml/XmlPullParser.cpp b/tools/aapt2/xml/XmlPullParser.cpp
index 30bdc50..402e5a4 100644
--- a/tools/aapt2/xml/XmlPullParser.cpp
+++ b/tools/aapt2/xml/XmlPullParser.cpp
@@ -141,17 +141,16 @@
   return event_queue_.front().data2;
 }
 
-Maybe<ExtractedPackage> XmlPullParser::TransformPackageAlias(
-    const StringPiece& alias, const StringPiece& local_package) const {
+Maybe<ExtractedPackage> XmlPullParser::TransformPackageAlias(const StringPiece& alias) const {
   if (alias.empty()) {
-    return ExtractedPackage{local_package.to_string(), false /* private */};
+    return ExtractedPackage{{}, false /*private*/};
   }
 
   const auto end_iter = package_aliases_.rend();
   for (auto iter = package_aliases_.rbegin(); iter != end_iter; ++iter) {
     if (alias == iter->prefix) {
       if (iter->package.package.empty()) {
-        return ExtractedPackage{local_package.to_string(), iter->package.private_namespace};
+        return ExtractedPackage{{}, iter->package.private_namespace};
       }
       return iter->package;
     }