stream: fix sync write perf regression

While nodejs#31046 did make async
writes faster it at the same time made sync writes slower.

This PR corrects this while maintaining performance improvements.

Author: ronag

lib/_stream_writable.js

@@ -421,27 +421,24 @@ function onwrite(stream, er) {
       onwriteError(stream, state, er, cb);
     }
   } else {
-    if (!state.destroyed) {
+    if (state.buffered.length > state.bufferedIndex) {
       clearBuffer(stream, state);
     }
-    if (state.needDrain || cb !== nop || state.ending || state.destroyed) {
-      if (sync) {
-        // It is a common case that the callback passed to .write() is always
-        // the same. In that case, we do not schedule a new nextTick(), but
-        // rather just increase a counter, to improve performance and avoid
-        // memory allocations.
-        if (state.afterWriteTickInfo !== null &&
-            state.afterWriteTickInfo.cb === cb) {
-          state.afterWriteTickInfo.count++;
-        } else {
-          state.afterWriteTickInfo = { count: 1, cb, stream, state };
-          process.nextTick(afterWriteTick, state.afterWriteTickInfo);
-        }
+
+    if (sync) {
+      // It is a common case that the callback passed to .write() is always
+      // the same. In that case, we do not schedule a new nextTick(), but
+      // rather just increase a counter, to improve performance and avoid
+      // memory allocations.
+      if (state.afterWriteTickInfo !== null &&
+          state.afterWriteTickInfo.cb === cb) {
+        state.afterWriteTickInfo.count++;
       } else {
-        afterWrite(stream, state, 1, cb);
+        state.afterWriteTickInfo = { count: 1, cb, stream, state };
+        process.nextTick(afterWriteTick, state.afterWriteTickInfo);
       }
     } else {
-      state.pendingcb--;
+      afterWrite(stream, state, 1, cb);
     }
   }
 }
@@ -489,7 +486,7 @@ function errorBuffer(state, err) {
 
 // If there's something in the buffer waiting, then process it
 function clearBuffer(stream, state) {
-  if (state.corked || state.bufferProcessing) {
+  if (state.corked || state.bufferProcessing || state.destroyed) {
     return;
   }