New Workload: mobx observer + startup (#151)

Sample application for using [mobx](https://github.com/mobxjs/mobx) state managed sometimes used in combination with react.

- Tuneable eval-reuse strategy
- Measuring startup
- Quite polymorphic

Author: camillobruni

mobx/benchmark-node.mjs

@@ -0,0 +1,7 @@
+import { runTest } from "./src/test.mjs";
+
+const then = performance.now();
+runTest();
+const duration = performance.now() - then;
+
+console.log(`Duration : ${duration.toFixed(2)}ms`);

mobx/benchmark.js

@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2025 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+const EXPECTED_LOG_LENGTH = 6824;
+
+class Benchmark extends StartupBenchmark {
+  lastResult;
+
+  constructor(iterationCount) {
+    super({
+      iterationCount,
+      expectedCacheCommentCount: 464,
+      sourceCodeReuseCount: 8,
+    });
+  }
+
+  runIteration(iteration) {
+    // Module is loaded into PrismJSBenchmark
+    let MobXBenchmark;
+    eval(this.iterationSourceCodes[iteration]);
+    this.lastResult = MobXBenchmark.runTest();
+  }
+
+  validate() {
+    console.assert(
+      this.lastResult.length === EXPECTED_LOG_LENGTH,
+      `Expected this.lastResult.length to be ${EXPECTED_LOG_LENGTH}, but got ${this.lastResult.length}`
+    );
+  }
+}