Add use counter for comma as separator in allow attribute.

Bug: 1062400
Change-Id: I787f4996c76946b53e67122672ef085036ee33c0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2323821Reviewed-by: Yoav Weiss <yoavweiss@chromium.org>
Commit-Queue: Ian Clelland <iclelland@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792348}

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

@@ -2687,6 +2687,7 @@ enum WebFeature {
   kV8PointerEvent_AltitudeAngle_AttributeGetter = 3352,
   kCrossBrowsingContextGroupMainFrameNulledNonEmptyNameAccessed = 3353,
   kPositionSticky = 3354,
+  kCommaSeparatorInAllowAttribute = 3355,
 
   // 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/html/html_iframe_element.cc

@@ -253,6 +253,10 @@ void HTMLIFrameElement::ParseAttribute(
         UseCounter::Count(GetDocument(),
                           WebFeature::kFeaturePolicyAllowAttribute);
       }
+      if (value.Contains(',')) {
+        UseCounter::Count(GetDocument(),
+                          WebFeature::kCommaSeparatorInAllowAttribute);
+      }
     }
   } else if (name == html_names::kDisallowdocumentaccessAttr &&
              RuntimeEnabledFeatures::DisallowDocumentAccessEnabled()) {

third_party/blink/renderer/core/html/html_iframe_element_test.cc

@@ -403,4 +403,20 @@ TEST_F(HTMLIFrameElementSimTest, AllowAttributeParsingError) {
       << ConsoleMessages().front();
 }
 
+TEST_F(HTMLIFrameElementSimTest, CommaSeparatorIsCounted) {
+  EXPECT_FALSE(
+      GetDocument().Loader()->GetUseCounterHelper().HasRecordedMeasurement(
+          WebFeature::kCommaSeparatorInAllowAttribute));
+  SimRequest main_resource("https://example.com", "text/html");
+  LoadURL("https://example.com");
+  main_resource.Complete(R"(
+    <iframe
+      allow="fullscreen, geolocation"></iframe>
+  )");
+
+  EXPECT_TRUE(
+      GetDocument().Loader()->GetUseCounterHelper().HasRecordedMeasurement(
+          WebFeature::kCommaSeparatorInAllowAttribute));
+}
+
 }  // namespace blink

tools/metrics/histograms/enums.xml

@@ -28553,6 +28553,7 @@ Called by update_use_counter_feature_enum.py.-->
   <int value="3353"
       label="CrossBrowsingContextGroupMainFrameNulledNonEmptyNameAccessed"/>
   <int value="3354" label="PositionSticky"/>
+  <int value="3355" label="CommaSeparatorInAllowAttribute"/>
 </enum>
 
 <enum name="FeaturePolicyAllowlistType">