Make inner classes static where possible

Change-Id: Icb75d765bd4e9198ef294c3d099c762a395a623e
diff --git a/gerrit-httpd/src/test/java/com/google/gerrit/httpd/raw/IndexServletTest.java b/gerrit-httpd/src/test/java/com/google/gerrit/httpd/raw/IndexServletTest.java
index 4a5bdc1..abf890e 100644
--- a/gerrit-httpd/src/test/java/com/google/gerrit/httpd/raw/IndexServletTest.java
+++ b/gerrit-httpd/src/test/java/com/google/gerrit/httpd/raw/IndexServletTest.java
@@ -22,7 +22,7 @@
 import org.junit.Test;
 
 public class IndexServletTest {
-  class TestIndexServlet extends IndexServlet {
+  static class TestIndexServlet extends IndexServlet {
     private static final long serialVersionUID = 1L;
 
     TestIndexServlet(String canonicalURL, String cdnPath) throws URISyntaxException {
diff --git a/gerrit-pgm/src/main/java/com/google/gerrit/pgm/http/jetty/ProjectQoSFilter.java b/gerrit-pgm/src/main/java/com/google/gerrit/pgm/http/jetty/ProjectQoSFilter.java
index f85a27a..4d2bb41 100644
--- a/gerrit-pgm/src/main/java/com/google/gerrit/pgm/http/jetty/ProjectQoSFilter.java
+++ b/gerrit-pgm/src/main/java/com/google/gerrit/pgm/http/jetty/ProjectQoSFilter.java
@@ -147,7 +147,7 @@
   @Override
   public void destroy() {}
 
-  private final class Listener implements ContinuationListener {
+  private static final class Listener implements ContinuationListener {
     final Future<?> future;
 
     Listener(Future<?> future) {
diff --git a/gerrit-server/src/test/java/com/google/gerrit/server/project/RefControlTest.java b/gerrit-server/src/test/java/com/google/gerrit/server/project/RefControlTest.java
index df4cb95..1fc95c1 100644
--- a/gerrit-server/src/test/java/com/google/gerrit/server/project/RefControlTest.java
+++ b/gerrit-server/src/test/java/com/google/gerrit/server/project/RefControlTest.java
@@ -895,7 +895,7 @@
     return all.get(local.getProject().getNameKey());
   }
 
-  private class MockUser extends CurrentUser {
+  private static class MockUser extends CurrentUser {
     private final String username;
     private final GroupMembership groups;