Part 2 of 5: Optimize the resource merge process, XmlProcessing.

Introduces the XmlDataResource and all the associated cruft that comes with parsing Android Resource value xmls: XmlValues, XmlValue.

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MOS_MIGRATED_REVID=116540181

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diff --git a/src/tools/android/java/com/google/devtools/build/android/XmlResourceValues.java b/src/tools/android/java/com/google/devtools/build/android/XmlResourceValues.java
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index 0000000000..1ed6631d1c
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+++ b/src/tools/android/java/com/google/devtools/build/android/XmlResourceValues.java
@@ -0,0 +1,216 @@
+// Copyright 2016 The Bazel Authors. All rights reserved.
+//
+// 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.
+package com.google.devtools.build.android;
+
+import com.google.devtools.build.android.xml.AttrXmlResourceValue;
+import com.google.devtools.build.android.xml.IdXmlResourceValue;
+import com.google.devtools.build.android.xml.PluralXmlResourceValue;
+import com.google.devtools.build.android.xml.SimpleXmlResourceValue;
+import com.google.devtools.build.android.xml.StyleXmlResourceValue;
+import com.google.devtools.build.android.xml.StyleableXmlResourceValue;
+
+import com.android.resources.ResourceType;
+
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import javax.xml.namespace.QName;
+import javax.xml.stream.XMLEventReader;
+import javax.xml.stream.XMLStreamException;
+import javax.xml.stream.events.Attribute;
+import javax.xml.stream.events.StartElement;
+import javax.xml.stream.events.XMLEvent;
+
+/**
+ * XmlValues provides methods for getting XmlValue derived classes.
+ *
+ * <p>Acts a static factory class containing the general xml parsing logic for resources
+ * that are declared inside the &lt;resources&gt; tag.
+ */
+public class XmlResourceValues {
+
+  private static final QName TAG_PLURALS = QName.valueOf("plurals");
+  private static final QName ATTR_QUANTITY = QName.valueOf("quantity");
+  private static final QName TAG_ATTR = QName.valueOf("attr");
+  private static final QName TAG_DECLARE_STYLEABLE = QName.valueOf("declare-styleable");
+  private static final QName TAG_ITEM = QName.valueOf("item");
+  private static final QName TAG_STYLE = QName.valueOf("style");
+  private static final QName TAG_RESOURCES = QName.valueOf("resources");
+  private static final QName ATTR_FORMAT = QName.valueOf("format");
+  private static final QName ATTR_NAME = QName.valueOf("name");
+  private static final QName ATTR_VALUE = QName.valueOf("value");
+  private static final QName ATTR_PARENT = QName.valueOf("parent");
+  private static final QName ATTR_TYPE = QName.valueOf("type");
+
+  static XmlResourceValue parsePlurals(XMLEventReader eventReader) throws XMLStreamException {
+    Map<String, String> values = new HashMap<>();
+    for (XMLEvent element = eventReader.nextTag();
+        !isEndTag(element, TAG_PLURALS);
+        element = eventReader.nextTag()) {
+      if (isItem(element)) {
+        values.put(
+            getElementAttributeByName(element.asStartElement(), ATTR_QUANTITY),
+            eventReader.getElementText());
+      }
+    }
+    return PluralXmlResourceValue.of(values);
+  }
+
+  static XmlResourceValue parseStyle(XMLEventReader eventReader, StartElement start)
+      throws XMLStreamException {
+    Map<String, String> values = new HashMap<>();
+    for (XMLEvent element = eventReader.nextTag();
+        !isEndTag(element, TAG_STYLE);
+        element = eventReader.nextTag()) {
+      if (isItem(element)) {
+        values.put(getElementName(element.asStartElement()), eventReader.getElementText());
+      }
+    }
+    return StyleXmlResourceValue.of(parseReferenceFromElementAttribute(start, ATTR_PARENT), values);
+  }
+
+  static void parseDeclareStyleable(
+      FullyQualifiedName.Factory fqnFactory,
+      Path path,
+      List<DataResource> nonOverwritable,
+      List<DataResource> overwritable,
+      XMLEventReader eventReader,
+      StartElement start)
+      throws XMLStreamException {
+    String styleableName = getElementName(start);
+    List<String> members = new ArrayList<>();
+    for (XMLEvent element = eventReader.nextTag();
+        !isEndTag(element, TAG_DECLARE_STYLEABLE);
+        element = eventReader.nextTag()) {
+      if (isStartTag(element, TAG_ATTR)) {
+        StartElement attr = element.asStartElement();
+        members.add(getElementName(attr));
+        String attrName = getElementName(attr);
+        overwritable.add(
+            XmlDataResource.of(
+                fqnFactory.create(ResourceType.ATTR, attrName),
+                path,
+                parseAttr(eventReader, start)));
+      }
+    }
+    nonOverwritable.add(
+        XmlDataResource.of(
+            fqnFactory.create(ResourceType.STYLEABLE, styleableName),
+            path,
+            StyleableXmlResourceValue.of(members)));
+  }
+
+  static XmlResourceValue parseAttr(XMLEventReader eventReader, StartElement start)
+      throws XMLStreamException {
+    return AttrXmlResourceValue.from(
+        start, getElementAttributeByName(start, ATTR_FORMAT), eventReader);
+  }
+
+  static XmlResourceValue parseId() {
+    return IdXmlResourceValue.of();
+  }
+
+  static XmlResourceValue parseSimple(XMLEventReader eventReader, ResourceType resourceType)
+      throws XMLStreamException {
+    return SimpleXmlResourceValue.of(
+        SimpleXmlResourceValue.Type.from(resourceType), eventReader.getElementText());
+  }
+
+  /* XML helper methods follow. */
+  // TODO(corysmith): Move these to a wrapper class for XMLEventReader.
+  private static String parseReferenceFromElementAttribute(StartElement element, QName name)
+      throws XMLStreamException {
+    String value = getElementAttributeByName(element, name);
+    if (value.startsWith("?") || value.startsWith("@")) {
+      return value.substring(1);
+    }
+    throw new XMLStreamException(
+        String.format("Invalid resource reference from %s in %s", name, element),
+        element.getLocation());
+  }
+
+  public static String getElementAttributeByName(StartElement element, QName name) {
+    Attribute attribute = element.getAttributeByName(name);
+    return attribute == null ? null : attribute.getValue();
+  }
+
+  public static String getElementValue(StartElement start) {
+    return getElementAttributeByName(start, ATTR_VALUE);
+  }
+
+  public static String getElementName(StartElement start) {
+    return getElementAttributeByName(start, ATTR_NAME);
+  }
+
+  public static String getElementType(StartElement start) {
+    return getElementAttributeByName(start, ATTR_TYPE);
+  }
+
+  public static boolean isTag(XMLEvent event, QName subTagType) {
+    if (event.isStartElement()) {
+      return isStartTag(event, subTagType);
+    }
+    if (event.isEndElement()) {
+      return isEndTag(event, subTagType);
+    }
+    return false;
+  }
+
+  public static boolean isItem(XMLEvent start) {
+    return isTag(start, TAG_ITEM);
+  }
+
+  public static boolean isEndTag(XMLEvent event, QName subTagType) {
+    if (event.isEndElement()) {
+      return subTagType.equals(event.asEndElement().getName());
+    }
+    return false;
+  }
+
+  public static boolean isStartTag(XMLEvent event, QName subTagType) {
+    if (event.isStartElement()) {
+      return subTagType.equals(event.asStartElement().getName());
+    }
+    return false;
+  }
+
+  public static XMLEvent peekNextTag(XMLEventReader eventReader) throws XMLStreamException {
+    while (!(eventReader.peek().isEndElement() || eventReader.peek().isStartElement())) {
+      eventReader.nextEvent();
+    }
+    return eventReader.peek();
+  }
+
+  static StartElement findNextStart(XMLEventReader eventReader) throws XMLStreamException {
+    while (eventReader.hasNext()) {
+      XMLEvent event = eventReader.nextEvent();
+      if (event.isStartElement()) {
+        return event.asStartElement();
+      }
+    }
+    return null;
+  }
+
+  static boolean moveToResources(XMLEventReader eventReader) throws XMLStreamException {
+    while (eventReader.hasNext()) {
+      if (findNextStart(eventReader).getName().equals(TAG_RESOURCES)) {
+        return true;
+      }
+    }
+    return false;
+  }
+}