Revert "Don't extend the return value of DelegateClass"

This reverts commit 4f61d46.

Author: amatsuda

activesupport/lib/active_support/cache/mem_cache_store.rb

@@ -36,7 +36,7 @@ def self.supports_cache_versioning?
       prepend Strategy::LocalCache
 
       module DupLocalCache
-        DupLocalStore = DelegateClass(Strategy::LocalCache::LocalStore) do
+        class DupLocalStore < DelegateClass(Strategy::LocalCache::LocalStore)
           def write_entry(_key, entry)
             if entry.is_a?(Entry)
               entry.dup_value!

activesupport/lib/active_support/syntax_error_proxy.rb

@@ -7,7 +7,7 @@ module ActiveSupport
   # is to enhance the backtraces on SyntaxError exceptions to include the
   # source location of the syntax error.  That way we can display the error
   # source on error pages in development.
-  SyntaxErrorProxy = DelegateClass(SyntaxError) do # :nodoc:
+  class SyntaxErrorProxy < DelegateClass(SyntaxError) # :nodoc:
     def backtrace
       parse_message_for_trace + super
     end
@@ -20,7 +20,7 @@ def label
       end
     end
 
-    BacktraceLocationProxy = DelegateClass(Thread::Backtrace::Location) do
+    class BacktraceLocationProxy < DelegateClass(Thread::Backtrace::Location)
       def initialize(loc, ex)
         super(loc)
         @ex = ex