Enable bulk writes in the HttpBlobStore

Second attempt of 0654620, which I am rolling back. The problem is that FilterOutputStream.write is just plain wrong and we shouldn't inherit FilterOutputStream at all, but instead do it manually (which actually requires less code).

This was a performance regression in deccc48.

Fixed #4944.

PiperOrigin-RevId: 191215696

Author: ulfjack

src/main/java/com/google/devtools/build/lib/remote/blobstore/http/HttpBlobStore.java

@@ -43,7 +43,6 @@
 import java.io.ByteArrayInputStream;
 import java.io.FileInputStream;
 import java.io.FilterInputStream;
-import java.io.FilterOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
@@ -199,23 +198,31 @@ public boolean get(String key, OutputStream out) throws IOException, Interrupted
   }
 
   @SuppressWarnings("FutureReturnValueIgnored")
-  private boolean get(String key, OutputStream out, boolean casDownload)
+  private boolean get(String key, final OutputStream out, boolean casDownload)
       throws IOException, InterruptedException {
     final AtomicBoolean dataWritten = new AtomicBoolean();
+
     OutputStream wrappedOut =
-        new FilterOutputStream(out) {
+        new OutputStream() {
+          // OutputStream.close() does nothing, which is what we want to ensure that the
+          // OutputStream can't be closed somewhere in the Netty pipeline, so that we can support
+          // retries. The OutputStream is closed in the finally block below.
+
+          @Override
+          public void write(byte[] b, int offset, int length) throws IOException {
+            dataWritten.set(true);
+            out.write(b, offset, length);
+          }
 
           @Override
           public void write(int b) throws IOException {
             dataWritten.set(true);
-            super.write(b);
+            out.write(b);
           }
 
           @Override
-          public void close() {
-            // Ensure that the OutputStream can't be closed somewhere in the Netty
-            // pipeline, so that we can support retries. The OutputStream is closed in
-            // the finally block below.
+          public void flush() throws IOException {
+            out.flush();
           }
         };
     DownloadCommand download = new DownloadCommand(uri, casDownload, key, wrappedOut);