Store IdTargetObserver::m_registry as a reference

Store IdTargetObserver::m_registry as a reference instead of a pointer.
This makes the code look safer and gets rid of an unnecessary null check.

Also make IdTargetObserverRegistry non copyable to protect against bad
assignments to references.

R=adamk@chromium.org, adamk, rwlbuis

Review URL: https://codereview.chromium.org/183463004

git-svn-id: svn://svn.chromium.org/blink/trunk@168419 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/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

third_party/WebKit/Source/core/dom/IdTargetObserver.h

@@ -41,7 +41,7 @@ protected:
     IdTargetObserver(IdTargetObserverRegistry&, const AtomicString& id);
 
 private:
-    IdTargetObserverRegistry* m_registry;
+    IdTargetObserverRegistry& m_registry;
     AtomicString m_id;
 };
 

third_party/WebKit/Source/core/dom/IdTargetObserverRegistry.h

@@ -37,7 +37,7 @@ namespace WebCore {
 class IdTargetObserver;
 
 class IdTargetObserverRegistry {
-    WTF_MAKE_FAST_ALLOCATED;
+    WTF_MAKE_NONCOPYABLE(IdTargetObserverRegistry); WTF_MAKE_FAST_ALLOCATED;
     friend class IdTargetObserver;
 public:
     static PassOwnPtr<IdTargetObserverRegistry> create();