Worker: Add use counters for WorkerOptions#type

This CL adds WebFeature::kClassicDedicatedWorker and
WebFeature::kModuleDedicatedWorker for WorkerOptions#type. These are
recorded in following cases.

(1) When a dedicated worker is constructed using classic scripts,
kClassicDedicatedWorker is recorded:

  const worker1 = new Worker('worker.js');  // or
  const worker2 = new Worker('worker.js', { type: 'classic' });

(2) When a dedicated worker is constructed using module scripts,
kModuleDedicatedWorker is recorded:

  const worker3 = new Worker('worker.js', { type: 'module' });

This CL adds web_tests for these cases.

In addition to that, this CL adds tests for existing kWorkerStart and
kNestedDedicatedWorker. kWorkerStart is recorded when a dedicated worker is
constructed regardless of given options (e.g., 'type') and creator's execution
context. kNestedDedicatedWorker is recorded when a dedicated worker is
constructed from another dedicated worker:

  const worker4 = new Worker('nested-worker.js');

  // In nested-worker.js
  const nested_worker = new Worker('worker.js');

Bug: 680046
Change-Id: Ic8aed3f9f43f6ceafeb5eac4a11382c7a21ea9b7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1906855
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714148}

third_party/blink/public/mojom/web_feature/web_feature.mojom

@@ -2465,6 +2465,8 @@ enum WebFeature {
   kHasGlyphRelativeUnits = 3081,
   kCountQueuingStrategyConstructor = 3082,
   kByteLengthQueuingStrategyConstructor = 3083,
+  kClassicDedicatedWorker = 3084,
+  kModuleDedicatedWorker = 3085,
 
   // Add new features immediately above this line. Don't change assigned
   // numbers of any item, and don't reuse removed slots.

third_party/blink/renderer/core/workers/README.md

@@ -112,6 +112,10 @@ There are some fundamental metrics.
 - [WorkerStart](https://www.chromestatus.com/metrics/feature/timeline/popularity/4)
 : Counts of `new DedicatedWorker()` calls in `Document` and
 `DedicatedWorkerGlobalScope`.
+- [ClassicDedicatedWorker](https://www.chromestatus.com/metrics/feature/timeline/popularity/3084)
+: Counts of new DedicatedWorker() calls with `{ type: 'classic' }` or without `WorkerOptions#type` argument.
+- [ModuleDedicatedWorker](https://www.chromestatus.com/metrics/feature/timeline/popularity/3085)
+: Counts of new DedicatedWorker() calls with `{ type: 'module' }`.
 - [NestedDedicatedWorker](https://www.chromestatus.com/metrics/feature/timeline/popularity/2499)
 : Counts of `new DedicatedWorker()` calls in `DedicatedWorkerGlobalScope`.
 - [SharedWorkerStart](https://www.chromestatus.com/metrics/feature/timeline/popularity/5)

third_party/blink/renderer/core/workers/dedicated_worker_messaging_proxy.cc

@@ -64,6 +64,8 @@ void DedicatedWorkerMessagingProxy::StartWorkerGlobalScope(
   if (options->type() == "classic") {
     // "classic: Fetch a classic worker script given url, outside settings,
     // destination, and inside settings."
+    UseCounter::Count(GetExecutionContext(),
+                      WebFeature::kClassicDedicatedWorker);
     switch (off_main_thread_fetch_option) {
       case OffMainThreadWorkerScriptFetchOption::kEnabled: {
         auto* resource_timing_notifier =
@@ -86,6 +88,8 @@ void DedicatedWorkerMessagingProxy::StartWorkerGlobalScope(
     // "module: Fetch a module worker script graph given url, outside settings,
     // destination, the value of the credentials member of options, and inside
     // settings."
+    UseCounter::Count(GetExecutionContext(),
+                      WebFeature::kModuleDedicatedWorker);
     network::mojom::CredentialsMode credentials_mode;
     bool result = Request::ParseCredentialsMode(options->credentials(),
                                                 &credentials_mode);

third_party/blink/web_tests/http/tests/workers/resources/nested-worker.js

+const worker = new Worker('empty.js');

third_party/blink/web_tests/http/tests/workers/worker-usecounter.html

+i<!DOCTYPE html>
+<title>Dedicated Worker: UseCounter</title>
+<script src="../../resources/testharness.js"></script>
+<script src="../../resources/testharnessreport.js"></script>
+<body>
+</body>
+<script>
+
+// From web_feature.mojom
+const kFeatureWorkerStart = 4;
+const kFeatureNestedDedicatedWorker = 2499;
+const kFeatureClassicDedicatedWorker = 3084;
+const kFeatureModuleDedicatedWorker = 3085;
+
+function isUseCounted(feature) {
+  return internals.isUseCounted(document, feature);
+}
+
+function observeUseCounter(feature) {
+  return internals.observeUseCounter(document, feature);
+}
+
+promise_test(async t => {
+  // Start a dedicated worker using classic scripts.
+  assert_false(isUseCounted(kFeatureWorkerStart));
+  assert_false(isUseCounted(kFeatureClassicDedicatedWorker));
+  const classic_worker = new Worker('resources/empty.js');
+  await Promise.all([
+      observeUseCounter(kFeatureWorkerStart),
+      observeUseCounter(kFeatureClassicDedicatedWorker)
+  ]);
+  assert_true(isUseCounted(kFeatureWorkerStart));
+  assert_true(isUseCounted(kFeatureClassicDedicatedWorker));
+
+  // Start a dedicated worker using module scripts.
+  assert_false(isUseCounted(kFeatureModuleDedicatedWorker));
+  const module_worker = new Worker('resources/empty.js', { type: 'module' });
+  await observeUseCounter(kFeatureModuleDedicatedWorker);
+  assert_true(isUseCounted(kFeatureModuleDedicatedWorker));
+
+  // Start a nested dedicated worker.
+  assert_false(isUseCounted(kFeatureNestedDedicatedWorker));
+  const nested_worker = new Worker('resources/nested-worker.js');
+  await observeUseCounter(kFeatureNestedDedicatedWorker);
+  assert_true(isUseCounted(kFeatureNestedDedicatedWorker));
+}, 'UseCounter on dedicated workers');
+
+</script>
+</html>

tools/metrics/histograms/enums.xml

@@ -25404,6 +25404,8 @@ Called by update_net_error_codes.py.-->
   <int value="3081" label="HasGlyphRelativeUnits"/>
   <int value="3082" label="CountQueuingStrategyConstructor"/>
   <int value="3083" label="ByteLengthQueuingStrategyConstructor"/>
+  <int value="3084" label="ClassicDedicatedWorker"/>
+  <int value="3085" label="ModuleDedicatedWorker"/>
 </enum>
 
 <enum name="FeaturePolicyAllowlistType">