HTTPHeaderMap: Favor composition over inheritance.

Source/platform/network/HTTPHeaderMap.cpp

Index: Source/platform/network/HTTPHeaderMap.cpp
diff --git a/Source/platform/network/HTTPHeaderMap.cpp b/Source/platform/network/HTTPHeaderMap.cpp
index a0644b5a7aad08e89a4b7a0a66fc4736ef71edd3..fa60bece3f6119fef10f50f694c1f9301ee5e7f8 100644
--- a/Source/platform/network/HTTPHeaderMap.cpp
+++ b/Source/platform/network/HTTPHeaderMap.cpp
@@ -63,16 +63,6 @@ void HTTPHeaderMap::adopt(PassOwnPtr<CrossThreadHTTPHeaderMapData> data)
     }
 }
 
-const AtomicString& HTTPHeaderMap::get(const AtomicString& name) const
-{
-    return HashMap<AtomicString, AtomicString, CaseFoldingHash>::get(name);
-}
-
-HTTPHeaderMap::AddResult HTTPHeaderMap::add(const AtomicString& name, const AtomicString& value)
-{
-    return HashMap<AtomicString, AtomicString, CaseFoldingHash>::add(name, value);
-}
-
 // Adapter that allows the HashMap to take C strings as keys.
 struct CaseFoldingCStringTranslator {
     static unsigned hash(const char* cString)
@@ -93,7 +83,7 @@ struct CaseFoldingCStringTranslator {
 
 const AtomicString& HTTPHeaderMap::get(const char* name) const
 {
-    const_iterator i = find<CaseFoldingCStringTranslator>(name);
+    const_iterator i = m_headers.find<CaseFoldingCStringTranslator>(name);
     if (i == end())
         return nullAtom;
     return i->value;
@@ -101,12 +91,12 @@ const AtomicString& HTTPHeaderMap::get(const char* name) const
 
 bool HTTPHeaderMap::contains(const char* name) const
 {
-    return find<CaseFoldingCStringTranslator>(name) != end();
+    return m_headers.find<CaseFoldingCStringTranslator>(name) != end();
 }
 
 HTTPHeaderMap::AddResult HTTPHeaderMap::add(const char* name, const AtomicString& value)
 {
-    return HashMap<AtomicString, AtomicString, CaseFoldingHash>::add<CaseFoldingCStringTranslator>(name, value);
+    return m_headers.add<CaseFoldingCStringTranslator>(name, value);
 }
 
 } // namespace blink