Convert some value classes to AutoValue

These classes were found by searching for custom hashCode
implementations, and omitting some cases:

 - Classes requiring custom serialization, which is not supported[1][2].
 - Most instances with custom hashCode or equals implementations,
   where the code savings is not as significant.
 - All classes in the extension API. We may migrate these eventually,
   but let's avoid this large backwards incompatible change until
   we're more used to AutoValue elsewhere.
 - All classes in the UI package.[3]

There are likely still more value classes that were missed by this
search that do not implement equals or hashCode.

[1] https://github.com/google/auto/tree/master/value#serialization
[2] This excludes, among other things, all persistent cache keys. It
might be possible to convert persistent caches to use a key
marshalling strategy other than Java serialization, but probably not
without invalidating all existing entries.
[3] This should still be possible as generated classes are generally
GWT compatible.

Change-Id: I96796b9879b7e487b80949b63115ac4032180f8b

gerrit-server/src/main/java/com/google/gerrit/server/util/LabelVote.java

@@ -16,18 +16,18 @@ package com.google.gerrit.server.util;
 
 import static com.google.common.base.Preconditions.checkArgument;
 
+import com.google.auto.value.AutoValue;
 import com.google.common.base.Strings;
 import com.google.gerrit.common.data.LabelType;
 import com.google.gerrit.reviewdb.client.PatchSetApproval;
 
-import java.util.Objects;
-
 /** A single vote on a label, consisting of a label name and a value. */
-public class LabelVote {
+@AutoValue
+public abstract class LabelVote {
   public static LabelVote parse(String text) {
     checkArgument(!Strings.isNullOrEmpty(text), "Empty label vote");
     if (text.charAt(0) == '-') {
-      return new LabelVote(text.substring(1), (short) 0);
+      return create(text.substring(1), (short) 0);
     }
     short sign = 0;
     int i;
@@ -44,9 +44,9 @@ public class LabelVote {
       }
     }
     if (sign == 0) {
-      return new LabelVote(text, (short) 1);
+      return create(text, (short) 1);
     }
-    return new LabelVote(text.substring(0, i),
+    return create(text.substring(0, i),
         (short)(sign * Short.parseShort(text.substring(i + 1))));
   }
 
@@ -54,63 +54,39 @@ public class LabelVote {
     checkArgument(!Strings.isNullOrEmpty(text), "Empty label vote");
     int e = text.lastIndexOf('=');
     checkArgument(e >= 0, "Label vote missing '=': %s", text);
-    return new LabelVote(text.substring(0, e),
+    return create(text.substring(0, e),
         Short.parseShort(text.substring(e + 1), text.length()));
   }
 
-  private final String name;
-  private final short value;
-
-  public LabelVote(String name, short value) {
-    this.name = LabelType.checkNameInternal(name);
-    this.value = value;
+  public static LabelVote create(String label, short value) {
+    return new AutoValue_LabelVote(LabelType.checkNameInternal(label), value);
   }
 
-  public LabelVote(PatchSetApproval psa) {
-    this(psa.getLabel(), psa.getValue());
+  public static LabelVote create(PatchSetApproval psa) {
+    return create(psa.getLabel(), psa.getValue());
   }
 
-  public String getLabel() {
-    return name;
-  }
-
-  public short getValue() {
-    return value;
-  }
+  public abstract String label();
+  public abstract short value();
 
   public String format() {
-    if (value == (short) 0) {
-      return '-' + name;
-    } else if (value < 0) {
-      return name + value;
+    if (value() == (short) 0) {
+      return '-' + label();
+    } else if (value() < 0) {
+      return label() + value();
     } else {
-      return name + '+' + value;
+      return label() + '+' + value();
     }
   }
 
   public String formatWithEquals() {
-    if (value <= (short) 0) {
-      return name + '=' + value;
+    if (value() <= (short) 0) {
+      return label() + '=' + value();
     } else {
-      return name + "=+" + value;
+      return label() + "=+" + value();
     }
   }
 
-  @Override
-  public boolean equals(Object o) {
-    if (o instanceof LabelVote) {
-      LabelVote l = (LabelVote) o;
-      return Objects.equals(name, l.name)
-          && value == l.value;
-    }
-    return false;
-  }
-
-  @Override
-  public int hashCode() {
-    return 17 * value  + name.hashCode();
-  }
-
   @Override
   public String toString() {
     return format();