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

Source/WebCore/dom/EventTarget.cpp

Index: Source/WebCore/dom/EventTarget.cpp
diff --git a/Source/WebCore/dom/EventTarget.cpp b/Source/WebCore/dom/EventTarget.cpp
index 3df5ba2f393c18310fc4f0011b9ef87f2cd27d8c..896481270eacadf871b41b353a5343522df150c6 100644
--- a/Source/WebCore/dom/EventTarget.cpp
+++ b/Source/WebCore/dom/EventTarget.cpp
@@ -211,11 +211,11 @@ bool EventTarget::fireEventListeners(Event* event)
             if (document->domWindow()) {
                 if (listenerPrefixedVector)
                     if (listenerUnprefixedVector)
-                        FeatureObserver::observe(document->domWindow(), FeatureObserver::PrefixedAndUnprefixedTransitionEndEvent);
+                        UseCounter::observe(document->domWindow(), UseCounter::PrefixedAndUnprefixedTransitionEndEvent);
                     else
-                        FeatureObserver::observe(document->domWindow(), FeatureObserver::PrefixedTransitionEndEvent);
+                        UseCounter::observe(document->domWindow(), UseCounter::PrefixedTransitionEndEvent);
                 else if (listenerUnprefixedVector)
-                    FeatureObserver::observe(document->domWindow(), FeatureObserver::UnprefixedTransitionEndEvent);
+                    UseCounter::observe(document->domWindow(), UseCounter::UnprefixedTransitionEndEvent);
             }
         }
     }