Merge branch 'stable-3.1' into stable-3.2

* stable-3.1:
  ContentTypeUtil: Add singleton scope
  Upgrade bazlets to latest stable-3.1 to build with 3.1.12 API
  Upgrade bazlets to latest stable-3.0 to build with 3.0.15 API
  Upgrade bazlets to latest stable-2.16 to build with 2.16.26 API
  Upgrade bazlets to latest stable-2.16 to build with 2.16.23 API

Change-Id: I64539e95e56258e182ff76e509cb8f7d22d5fd9d

src/main/java/com/googlesource/gerrit/plugins/uploadvalidator/ContentTypeUtil.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/uploadvalidator/ContentTypeUtil.java b/src/main/java/com/googlesource/gerrit/plugins/uploadvalidator/ContentTypeUtil.java
index bb6f9db..517d245 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/uploadvalidator/ContentTypeUtil.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/uploadvalidator/ContentTypeUtil.java
@@ -24,6 +24,7 @@
 import com.google.gerrit.server.config.ProjectConfigEntry;
 import com.google.inject.AbstractModule;
 import com.google.inject.Inject;
+import com.google.inject.Scopes;
 import com.google.inject.name.Named;
 import java.io.IOException;
 import java.io.InputStream;
@@ -41,7 +42,7 @@
 
       @Override
       protected void configure() {
-        bind(ContentTypeUtil.class);
+        bind(ContentTypeUtil.class).in(Scopes.SINGLETON);
         bind(ProjectConfigEntry.class)
             .annotatedWith(Exports.named(KEY_BINARY_TYPES))
             .toInstance(