[inspector] test to check that we don't hold resolved promises

Bug: v8:6197
Change-Id: I7b9e6d0979630dfd1ce5ee7f23f715cdb2f51802
R: dgozman@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/524045Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45746}

test/inspector/debugger/not-hold-promises-expected.txt

+Tests that we don't hold promises.
+SUCCESS

test/inspector/debugger/not-hold-promises.js

+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+let {session, contextGroup, Protocol} =
+  InspectorTest.start('Tests that we don\'t hold promises.');
+
+(async function test() {
+  Protocol.Runtime.enable();
+  Protocol.Debugger.enable();
+  Protocol.Debugger.setAsyncCallStackDepth({maxDepth: 128});
+  Protocol.HeapProfiler.enable();
+  // Force inspector internal scripts compilation.
+  await Protocol.Runtime.evaluate({expression: ''});
+  let snapshot = '';
+  Protocol.HeapProfiler.onAddHeapSnapshotChunk(msg => snapshot += msg.params.chunk);
+  await Protocol.HeapProfiler.collectGarbage();
+  await Protocol.HeapProfiler.takeHeapSnapshot();
+  let initial_node_count = JSON.parse(snapshot).snapshot.node_count;
+
+  await Protocol.Runtime.evaluate({
+    expression: `for (let i = 0; i < ${initial_node_count / 4}; ++i) Promise.resolve()`});
+  snapshot = '';
+  Protocol.HeapProfiler.onAddHeapSnapshotChunk(msg => snapshot += msg.params.chunk);
+  await Protocol.HeapProfiler.collectGarbage();
+  await Protocol.HeapProfiler.takeHeapSnapshot();
+  let without_storing_node_count = JSON.parse(snapshot).snapshot.node_count;
+  let diff_without_storing = (without_storing_node_count - initial_node_count);
+
+  if (diff_without_storing < initial_node_count / 4) {
+    InspectorTest.log('SUCCESS');
+  } else {
+    InspectorTest.log('FAILED: looks like all promises were not collected.');
+  }
+  InspectorTest.completeTest();
+})();