Rename FeatureObserver to UseCounter to make clear that all it stores are usage counts.

Source/WebCore/html/TextInputType.cpp

Index: Source/WebCore/html/TextInputType.cpp
diff --git a/Source/WebCore/html/TextInputType.cpp b/Source/WebCore/html/TextInputType.cpp
index f7a9b589b2569115cbb9f30561aed03eec5be8d9..556f471f61acf9d38a28f59b7ba7c74dd38985b7 100644
--- a/Source/WebCore/html/TextInputType.cpp
+++ b/Source/WebCore/html/TextInputType.cpp
@@ -49,9 +49,9 @@ void TextInputType::attach()
     TextFieldInputType::attach();
     const AtomicString& type = element()->fastGetAttribute(typeAttr);
     if (equalIgnoringCase(type, InputTypeNames::datetime()))
-        observeFeatureIfVisible(FeatureObserver::InputTypeDateTimeFallback);
+        observeFeatureIfVisible(UseCounter::InputTypeDateTimeFallback);
     else if (equalIgnoringCase(type, InputTypeNames::week()))
-        observeFeatureIfVisible(FeatureObserver::InputTypeWeekFallback);
+        observeFeatureIfVisible(UseCounter::InputTypeWeekFallback);
 }
 
 const AtomicString& TextInputType::formControlType() const