Migrate httpd classes to Flogger

This is the first part of the migration to Flogger. This change
migrates all classes of the 'http' module to Flogger. Other modules
continue to use slf4j. They should be migrated by follow-up changes.

During this migration we try to make the log statements more consistent:
- avoid string concatenation
- avoid usage of String.format(...)

Change-Id: I473c41733b00aa1ceab92fe0dc8cd1c6b347174c
Signed-off-by: Edwin Kempin <ekempin@google.com>

java/com/google/gerrit/httpd/RunAsFilter.java

@@ -18,6 +18,7 @@ import static com.google.gerrit.httpd.restapi.RestApiServlet.replyError;
 import static javax.servlet.http.HttpServletResponse.SC_FORBIDDEN;
 import static javax.servlet.http.HttpServletResponse.SC_INTERNAL_SERVER_ERROR;
 
+import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.extensions.registration.DynamicItem;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.reviewdb.client.Account;
@@ -41,13 +42,11 @@ import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import org.eclipse.jgit.errors.ConfigInvalidException;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 /** Allows running a request as another user account. */
 @Singleton
 class RunAsFilter implements Filter {
-  private static final Logger log = LoggerFactory.getLogger(RunAsFilter.class);
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
   private static final String RUN_AS = "X-Gerrit-RunAs";
 
   static class Module extends ServletModule {
@@ -99,7 +98,7 @@ class RunAsFilter implements Filter {
         replyError(req, res, SC_FORBIDDEN, "not permitted to use " + RUN_AS, null);
         return;
       } catch (PermissionBackendException e) {
-        log.warn("cannot check runAs", e);
+        logger.atWarning().withCause(e).log("cannot check runAs");
         replyError(req, res, SC_INTERNAL_SERVER_ERROR, RUN_AS + " unavailable", null);
         return;
       }
@@ -108,7 +107,7 @@ class RunAsFilter implements Filter {
       try {
         target = accountResolver.find(runas);
       } catch (OrmException | IOException | ConfigInvalidException e) {
-        log.warn("cannot resolve account for " + RUN_AS, e);
+        logger.atWarning().withCause(e).log("cannot resolve account for %s", RUN_AS);
         replyError(req, res, SC_INTERNAL_SERVER_ERROR, "cannot resolve " + RUN_AS, e);
         return;
       }