Replace FileInputStream and FileOutputStream with static Files methods

FileInputStream and FileOutputStream rely on finalize() method to ensure
resources are closed. This implies they are added to the finalizer queue
which causes additional work for the JVM GC process.

This is an open bug on the OpenJDK [1] and the recommended workaround is
to use the Files.newInputStream and Files.newOutputStream static methods
instead.

[1] https://bugs.openjdk.java.net/browse/JDK-8080225

Change-Id: I3cef6fcf198dde2be7cd15bded8d2fa247177654

gerrit-war/src/main/java/com/google/gerrit/httpd/UnzippedDistribution.java

@@ -20,10 +20,10 @@ import static com.google.gerrit.pgm.init.InitPlugins.PLUGIN_DIR;
 import com.google.gerrit.pgm.init.PluginsDistribution;
 import com.google.inject.Singleton;
 import java.io.File;
-import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.file.Files;
 import java.util.ArrayList;
 import java.util.List;
 import javax.servlet.ServletContext;
@@ -45,7 +45,7 @@ class UnzippedDistribution implements PluginsDistribution {
       for (File p : list) {
         String pluginJarName = p.getName();
         String pluginName = pluginJarName.substring(0, pluginJarName.length() - JAR.length());
-        try (InputStream in = new FileInputStream(p)) {
+        try (InputStream in = Files.newInputStream(p.toPath())) {
           processor.process(pluginName, in);
         }
       }