Use C++11 range-based loop for core/clipboard, core/dom and core/testing

Source/core/dom/MutationObserverRegistration.cpp

Index: Source/core/dom/MutationObserverRegistration.cpp
diff --git a/Source/core/dom/MutationObserverRegistration.cpp b/Source/core/dom/MutationObserverRegistration.cpp
index 0a29b207f18052bbdef2d70042e07537aa6003cd..0162fc19274dc4a150464f28f166434f4b74af1d 100644
--- a/Source/core/dom/MutationObserverRegistration.cpp
+++ b/Source/core/dom/MutationObserverRegistration.cpp
@@ -97,8 +97,8 @@ void MutationObserverRegistration::clearTransientRegistrations()
         return;
     }
 
-    for (NodeHashSet::iterator iter = m_transientRegistrationNodes->begin(); iter != m_transientRegistrationNodes->end(); ++iter)
-        (*iter)->unregisterTransientMutationObserver(this);
+    for (auto node : *m_transientRegistrationNodes)
+        node->unregisterTransientMutationObserver(this);
 
     m_transientRegistrationNodes.clear();