AAPT2: Fail compiling when private symbols are referenced

Also moved some XML specific stuff into its own directory,
and refactored ReferenceLinker a bit.

Change-Id: I912247a82023c1bbf72dc191fbdaf62858cbec0c
diff --git a/tools/aapt2/xml/XmlDom_test.cpp b/tools/aapt2/xml/XmlDom_test.cpp
new file mode 100644
index 0000000..431ee2c
--- /dev/null
+++ b/tools/aapt2/xml/XmlDom_test.cpp
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "xml/XmlDom.h"
+
+#include <gtest/gtest.h>
+#include <sstream>
+#include <string>
+
+namespace aapt {
+
+constexpr const char* kXmlPreamble = "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n";
+
+TEST(XmlDomTest, Inflate) {
+    std::stringstream in(kXmlPreamble);
+    in << R"EOF(
+        <Layout xmlns:android="http://schemas.android.com/apk/res/android"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content">
+            <TextView android:id="@+id/id"
+                      android:layout_width="wrap_content"
+                      android:layout_height="wrap_content" />
+        </Layout>
+    )EOF";
+
+    const Source source = { "test.xml" };
+    StdErrDiagnostics diag;
+    std::unique_ptr<xml::XmlResource> doc = xml::inflate(&in, &diag, source);
+    ASSERT_NE(doc, nullptr);
+
+    xml::Namespace* ns = xml::nodeCast<xml::Namespace>(doc->root.get());
+    ASSERT_NE(ns, nullptr);
+    EXPECT_EQ(ns->namespaceUri, u"http://schemas.android.com/apk/res/android");
+    EXPECT_EQ(ns->namespacePrefix, u"android");
+}
+
+} // namespace aapt