Add use counter for ::target-text

The counter counts the usage of matching non-UA rules with
::target-text.

Bug: 1168273, 1136817
Change-Id: I784680927b62dbd592eb1d05bef5e6edb76805d3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2640255Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845336}

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

@@ -3102,6 +3102,7 @@ enum WebFeature {
   kV8TCPSocket_Writable_AttributeGetter = 3777,
   kV8TCPSocket_RemoteAddress_AttributeGetter = 3778,
   kV8TCPSocket_RemotePort_AttributeGetter = 3779,
+  kCSSSelectorTargetText = 3780,
 
   // 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/css/selector_checker.cc

@@ -1112,6 +1112,12 @@ bool SelectorChecker::CheckPseudoElement(const SelectorCheckingContext& context,
         return false;
       return true;
     }
+    case CSSSelector::kPseudoTargetText:
+      if (!is_ua_rule_) {
+        UseCounter::Count(context.element->GetDocument(),
+                          WebFeature::kCSSSelectorTargetText);
+      }
+      FALLTHROUGH;
     default:
       DCHECK_NE(mode_, kQueryingRules);
       result.dynamic_pseudo =

third_party/blink/renderer/core/css/selector_checker.h

@@ -90,11 +90,8 @@ class CORE_EXPORT SelectorChecker {
         scrollbar_(init.scrollbar),
         part_names_(init.part_names),
         scrollbar_part_(init.scrollbar_part),
-        mode_(init.mode) {
-#if DCHECK_IS_ON()
-    is_ua_rule_ = init.is_ua_rule;
-#endif
-  }
+        mode_(init.mode),
+        is_ua_rule_(init.is_ua_rule) {}
   SelectorChecker(const SelectorChecker&) = delete;
   SelectorChecker& operator=(const SelectorChecker&) = delete;
 
@@ -194,11 +191,9 @@ class CORE_EXPORT SelectorChecker {
   PartNames* part_names_;
   ScrollbarPart scrollbar_part_;
   Mode mode_;
+  bool is_ua_rule_;
 #if DCHECK_IS_ON()
   mutable bool inside_match_ = false;
-  bool is_ua_rule_;
-#else
-  static constexpr bool is_ua_rule_ = true;
 #endif
 };
 

third_party/blink/renderer/core/css/style_engine_test.cc

@@ -4067,4 +4067,28 @@ TEST_F(StyleEngineTest, AudioUAStyleNameSpace) {
   EXPECT_FALSE(html_audio->GetComputedStyle());
 }
 
+TEST_F(StyleEngineTest, TargetTextUseCount) {
+  ClearUseCounter(WebFeature::kCSSSelectorTargetText);
+  GetDocument().body()->setInnerHTML(R"HTML(
+    <style>
+      #nevermatch::target-text { background-color: pink }
+    </style>
+  )HTML");
+  UpdateAllLifecyclePhases();
+  EXPECT_FALSE(IsUseCounted(WebFeature::kCSSSelectorTargetText));
+  ClearUseCounter(WebFeature::kCSSSelectorTargetText);
+
+  // Count ::target-text if we would have matched if the page was loaded with a
+  // text fragment url.
+  GetDocument().body()->setInnerHTML(R"HTML(
+    <style>
+      div::target-text { background-color: pink }
+    </style>
+    <div></div>
+  )HTML");
+  UpdateAllLifecyclePhases();
+  EXPECT_TRUE(IsUseCounted(WebFeature::kCSSSelectorTargetText));
+  ClearUseCounter(WebFeature::kCSSSelectorTargetText);
+}
+
 }  // namespace blink

tools/metrics/histograms/enums.xml

@@ -31021,6 +31021,7 @@ Called by update_use_counter_feature_enum.py.-->
   <int value="3777" label="V8TCPSocket_Writable_AttributeGetter"/>
   <int value="3778" label="V8TCPSocket_RemoteAddress_AttributeGetter"/>
   <int value="3779" label="V8TCPSocket_RemotePort_AttributeGetter"/>
+  <int value="3780" label="CSSSelectorTargetText"/>
 </enum>
 
 <enum name="FeaturePolicyAllowlistType">