Store IdTargetObserver::m_registry as a reference

Source/core/dom/IdTargetObserver.cpp

Index: Source/core/dom/IdTargetObserver.cpp
diff --git a/Source/core/dom/IdTargetObserver.cpp b/Source/core/dom/IdTargetObserver.cpp
index 69579955c7564cd5f9244ac196439f740626256a..af185a0ad05e3f1e0ec151c32160a60d76acfb46 100644
--- a/Source/core/dom/IdTargetObserver.cpp
+++ b/Source/core/dom/IdTargetObserver.cpp
@@ -31,16 +31,15 @@
 namespace WebCore {
 
 IdTargetObserver::IdTargetObserver(IdTargetObserverRegistry& registry, const AtomicString& id)
-    : m_registry(&registry)
+    : m_registry(registry)
     , m_id(id)
 {
-    m_registry->addObserver(m_id, this);
+    m_registry.addObserver(m_id, this);
 }
 
 IdTargetObserver::~IdTargetObserver()
 {
-    if (m_registry)
-        m_registry->removeObserver(m_id, this);
+    m_registry.removeObserver(m_id, this);
 }
 
 } // namespace WebCore