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

Source/bindings/scripts/CodeGeneratorV8.pm

 # Copyright (C) 2005, 2006 Nikolas Zimmermann <zimmermann@kde.org>
 # Copyright (C) 2006 Anders Carlsson <andersca@mac.com>
 # Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
 # Copyright (C) 2006 Alexey Proskuryakov <ap@webkit.org>
 # Copyright (C) 2006 Apple Computer, Inc.
 # Copyright (C) 2007, 2008, 2009, 2012 Google Inc.
 # Copyright (C) 2009 Cameron McCormack <cam@mcc.id.au>
 # Copyright (C) Research In Motion Limited 2010. All rights reserved.
 # Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
 # Copyright (C) 2012 Ericsson AB. All rights reserved.
@@ skipping 893 matching lines @@
     return perContextData->constructorForType(WrapperTypeInfo::unwrap(data));
 }
 END
 }
 
 sub GenerateFeatureObservation
 {
     my $measureAs = shift;
 
     if ($measureAs) {
-        AddToImplIncludes("FeatureObserver.h");
-        return "    FeatureObserver::observe(activeDOMWindow(BindingState::instance()), FeatureObserver::${measureAs});\n";
+        AddToImplIncludes("UseCounter.h");
+        return "    UseCounter::observe(activeDOMWindow(BindingState::instance()), UseCounter::${measureAs});\n";
     }
 
     return "";
 }
 
 sub GenerateNormalAttrGetterCallback
 {
     my $attribute = shift;
     my $interface = shift;
     my $forMainWorldSuffix = shift;
@@ skipping 3670 matching lines @@
 
 sub GetPassRefPtrType
 {
     my $v8InterfaceName = shift;
 
     my $angleBracketSpace = $v8InterfaceName =~ />$/ ? " " : "";
     return "PassRefPtr<${v8InterfaceName}${angleBracketSpace}>";
 }
 
 1;