[analysis server] Keep more of the recent requests

* Bump kept requests from 50 to 250
* Make the request storage (`RecentBuffer`) add in constant time instead
  of linear time (modulo the `n` in `O(n)` being the constant 50 or 250
  making the before theoretically constant too, but anyway).

Change-Id: Ib00bd038b06f167fd7298a87402a89a23fd53880
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/457025
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Jens Johansen <[email protected]>

Author: jensjoha

pkg/analysis_server/lib/src/analysis_server.dart

@@ -1305,7 +1305,7 @@ enum MessageType {
 
 class ServerRecentPerformance {
   /// The maximum number of performance measurements to keep.
-  static const int performanceListMaxLength = 50;
+  static const int performanceListMaxLength = 250;
 
   /// The maximum number of slow performance measurements to keep.
   static const int slowRequestsListMaxLength = 1000;

pkg/analysis_server/lib/src/collections.dart

@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'dart:collection';
+
 /// Returns the given [list] if it is not empty, or `null` otherwise.
 List<E>? nullIfEmpty<E>(List<E>? list) {
   if (list == null || list.isEmpty) {
@@ -17,17 +19,16 @@ List<E>? nullIfEmpty<E>(List<E>? list) {
 class RecentBuffer<T> {
   final int capacity;
 
-  final List<T> _buffer = [];
+  final Queue<T> _buffer;
 
-  RecentBuffer(this.capacity);
+  RecentBuffer(this.capacity) : _buffer = Queue();
 
-  Iterable<T> get items => _buffer.reversed;
+  Iterable<T> get items => _buffer;
 
   void add(T item) {
-    _buffer.add(item);
-
-    if (_buffer.length > capacity) {
-      _buffer.removeAt(0);
+    while (_buffer.length >= capacity) {
+      _buffer.removeLast();
     }
+    _buffer.addFirst(item);
   }
 }