[Layered API] Add UseCounters for each individual modules

Bug: 829084
Change-Id: I699e5e8ac655f1b305fff5985a107d29f2200fce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1506825Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Commit-Queue: Hiroshige Hayashizaki <hiroshige@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638509}

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

@@ -2255,6 +2255,8 @@ enum WebFeature {
   kCSSValueAppearanceTextarea = 2821,
   kCSSValueAppearanceTextFieldForOthersRendered = 2822,
   kCSSValueAppearanceTextFieldForTemporalRendered = 2823,
+  kBuiltInModuleKvStorage = 2824,
+  kBuiltInModuleVirtualScroller = 2825,
 
   // 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/script/layered_api.cc

@@ -23,18 +23,21 @@ static const char kImportScheme[] = "import";
 
 constexpr char kBuiltinSpecifierPrefix[] = "@std/";
 
-int GetResourceIDFromPath(const Modulator& modulator, const String& path) {
+constexpr char kTopLevelScriptPostfix[] = "/index.js";
+
+const LayeredAPIResource* GetResourceFromPath(const Modulator& modulator,
+                                              const String& path) {
   for (size_t i = 0; i < base::size(kLayeredAPIResources); ++i) {
     if (modulator.BuiltInModuleEnabled(kLayeredAPIResources[i].module) &&
         path == kLayeredAPIResources[i].path) {
-      return kLayeredAPIResources[i].resource_id;
+      return &kLayeredAPIResources[i];
     }
   }
-  return -1;
+  return nullptr;
 }
 
 bool IsImplemented(const Modulator& modulator, const String& name) {
-  return GetResourceIDFromPath(modulator, name + "/index.js") >= 0;
+  return GetResourceFromPath(modulator, name + kTopLevelScriptPostfix);
 }
 
 }  // namespace
@@ -104,11 +107,15 @@ String GetSourceText(const Modulator& modulator, const KURL& url) {
     path = path.Substring(2);
   }
 
-  int resource_id = GetResourceIDFromPath(modulator, path);
-  if (resource_id < 0)
+  const LayeredAPIResource* resource = GetResourceFromPath(modulator, path);
+  if (!resource)
     return String();
 
-  return UncompressResourceAsString(resource_id);
+  // Only count the use of top-level scripts of each built-in module.
+  if (path.EndsWith(kTopLevelScriptPostfix))
+    modulator.BuiltInModuleUseCount(resource->module);
+
+  return UncompressResourceAsString(resource->resource_id);
 }
 
 }  // namespace layered_api

third_party/blink/renderer/core/script/modulator.h

@@ -123,6 +123,7 @@ class CORE_EXPORT Modulator : public GarbageCollectedFinalized<Modulator>,
 
   virtual bool BuiltInModuleInfraEnabled() const = 0;
   virtual bool BuiltInModuleEnabled(blink::layered_api::Module) const = 0;
+  virtual void BuiltInModuleUseCount(blink::layered_api::Module) const = 0;
 
   // https://html.spec.whatwg.org/C/#fetch-a-module-script-tree
   // https://html.spec.whatwg.org/C/#fetch-a-module-worker-script-tree

third_party/blink/renderer/core/script/modulator_impl_base.cc

@@ -65,6 +65,24 @@ bool ModulatorImplBase::BuiltInModuleEnabled(
   }
 }
 
+void ModulatorImplBase::BuiltInModuleUseCount(
+    blink::layered_api::Module module) const {
+  DCHECK(BuiltInModuleInfraEnabled());
+  DCHECK(BuiltInModuleEnabled(module));
+  switch (module) {
+    case blink::layered_api::Module::kBlank:
+      break;
+    case blink::layered_api::Module::kVirtualScroller:
+      UseCounter::Count(GetExecutionContext(),
+                        WebFeature::kBuiltInModuleVirtualScroller);
+      break;
+    case blink::layered_api::Module::kKvStorage:
+      UseCounter::Count(GetExecutionContext(),
+                        WebFeature::kBuiltInModuleKvStorage);
+      break;
+  }
+}
+
 // <specdef label="fetch-a-module-script-tree"
 // href="https://html.spec.whatwg.org/C/#fetch-a-module-script-tree">
 // <specdef label="fetch-a-module-worker-script-tree"

third_party/blink/renderer/core/script/modulator_impl_base.h

@@ -44,6 +44,7 @@ class ModulatorImplBase : public Modulator {
 
   bool BuiltInModuleInfraEnabled() const override;
   bool BuiltInModuleEnabled(blink::layered_api::Module) const override;
+  void BuiltInModuleUseCount(blink::layered_api::Module) const override;
 
   ScriptModuleResolver* GetScriptModuleResolver() override {
     return script_module_resolver_.Get();

third_party/blink/renderer/core/testing/dummy_modulator.cc

@@ -66,6 +66,8 @@ bool DummyModulator::BuiltInModuleEnabled(blink::layered_api::Module) const {
   return false;
 }
 
+void DummyModulator::BuiltInModuleUseCount(blink::layered_api::Module) const {}
+
 ScriptModuleResolver* DummyModulator::GetScriptModuleResolver() {
   return resolver_.Get();
 }

third_party/blink/renderer/core/testing/dummy_modulator.h

@@ -37,6 +37,7 @@ class DummyModulator : public Modulator {
 
   bool BuiltInModuleInfraEnabled() const override;
   bool BuiltInModuleEnabled(blink::layered_api::Module) const override;
+  void BuiltInModuleUseCount(blink::layered_api::Module) const override;
 
   void FetchTree(const KURL&,
                  ResourceFetcher*,

tools/metrics/histograms/enums.xml

@@ -21792,6 +21792,8 @@ Called by update_net_error_codes.py.-->
   <int value="2821" label="CSSValueAppearanceTextarea"/>
   <int value="2822" label="CSSValueAppearanceTextFieldForOthersRendered"/>
   <int value="2823" label="CSSValueAppearanceTextFieldForTemporalRendered"/>
+  <int value="2824" label="BuiltInModuleKvStorage"/>
+  <int value="2825" label="BuiltInModuleVirtualScroller"/>
 </enum>
 
 <enum name="FeaturePolicyFeature">