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/XmlPullParser_test.cpp b/tools/aapt2/xml/XmlPullParser_test.cpp
new file mode 100644
index 0000000..8fa2c6d
--- /dev/null
+++ b/tools/aapt2/xml/XmlPullParser_test.cpp
@@ -0,0 +1,55 @@
+/*
+ * 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 "util/StringPiece.h"
+#include "xml/XmlPullParser.h"
+
+#include <gtest/gtest.h>
+#include <sstream>
+
+namespace aapt {
+
+TEST(XmlPullParserTest, NextChildNodeTraversesCorrectly) {
+    std::stringstream str;
+    str << "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n"
+            "<a><b><c xmlns:a=\"http://schema.org\"><d/></c><e/></b></a>";
+    xml::XmlPullParser parser(str);
+
+    const size_t depthOuter = parser.getDepth();
+    ASSERT_TRUE(xml::XmlPullParser::nextChildNode(&parser, depthOuter));
+
+    EXPECT_EQ(xml::XmlPullParser::Event::kStartElement, parser.getEvent());
+    EXPECT_EQ(StringPiece16(u"a"), StringPiece16(parser.getElementName()));
+
+    const size_t depthA = parser.getDepth();
+    ASSERT_TRUE(xml::XmlPullParser::nextChildNode(&parser, depthA));
+    EXPECT_EQ(xml::XmlPullParser::Event::kStartElement, parser.getEvent());
+    EXPECT_EQ(StringPiece16(u"b"), StringPiece16(parser.getElementName()));
+
+    const size_t depthB = parser.getDepth();
+    ASSERT_TRUE(xml::XmlPullParser::nextChildNode(&parser, depthB));
+    EXPECT_EQ(xml::XmlPullParser::Event::kStartElement, parser.getEvent());
+    EXPECT_EQ(StringPiece16(u"c"), StringPiece16(parser.getElementName()));
+
+    ASSERT_TRUE(xml::XmlPullParser::nextChildNode(&parser, depthB));
+    EXPECT_EQ(xml::XmlPullParser::Event::kStartElement, parser.getEvent());
+    EXPECT_EQ(StringPiece16(u"e"), StringPiece16(parser.getElementName()));
+
+    ASSERT_FALSE(xml::XmlPullParser::nextChildNode(&parser, depthOuter));
+    EXPECT_EQ(xml::XmlPullParser::Event::kEndDocument, parser.getEvent());
+}
+
+} // namespace aapt