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

Source/WebCore/html/InputType.cpp

Index: Source/WebCore/html/InputType.cpp
diff --git a/Source/WebCore/html/InputType.cpp b/Source/WebCore/html/InputType.cpp
index 3ad1d98cd2db517860862781d58624eb091053a9..bfc19d5b43057f1d5dbd887ae871f2801c9708a7 100644
--- a/Source/WebCore/html/InputType.cpp
+++ b/Source/WebCore/html/InputType.cpp
@@ -1120,11 +1120,11 @@ void InputType::stepUpFromRenderer(int n)
     }
 }
 
-void InputType::observeFeatureIfVisible(FeatureObserver::Feature feature) const
+void InputType::observeFeatureIfVisible(UseCounter::Feature feature) const
 {
     if (RenderStyle* style = element()->renderStyle()) {
         if (style->visibility() != HIDDEN)
-            FeatureObserver::observe(element()->document(), feature);
+            UseCounter::observe(element()->document(), feature);
     }
 }