Add the possibility to have several behaviors in AS::Deprecation.

activesupport/lib/active_support/deprecation/behaviors.rb

 require "active_support/notifications"
+require "active_support/core_ext/array/wrap"
 
 module ActiveSupport
   module Deprecation
@@ -11,7 +12,7 @@ def behavior
       end
 
       def behavior=(behavior)
-        @behavior = DEFAULT_BEHAVIORS[behavior] || behavior
+        @behavior = Array.wrap(behavior).map { |b| DEFAULT_BEHAVIORS[b] || b }
       end
     end
 

activesupport/lib/active_support/deprecation/reporting.rb

@@ -4,8 +4,9 @@ class << self
       attr_accessor :silenced
 
       def warn(message = nil, callstack = caller)
-        if behavior && !silenced
-          behavior.call(deprecation_message(callstack, message), callstack)
+        return if silenced
+        deprecation_message(callstack, message).tap do |m|
+          behavior.each { |b| b.call(m, callstack) }
         end
       end
 

activesupport/lib/active_support/i18n_railtie.rb

 require "active_support"
 require "rails"
 require "active_support/file_update_checker"
+require "active_support/core_ext/array/wrap"
 
 module I18n
   class Railtie < Rails::Railtie

activesupport/test/deprecation_test.rb

@@ -80,6 +80,19 @@ def test_nil_behavior_is_ignored
     assert_deprecated(/foo=nil/) { @dtc.partially }
   end
 
+  def test_several_behaviors
+    @a, @b = nil, nil
+
+    ActiveSupport::Deprecation.behavior = [
+      Proc.new { |msg, callstack| @a = msg },
+      Proc.new { |msg, callstack| @b = msg }
+    ]
+
+    @dtc.partially
+    assert_match(/foo=nil/, @a)
+    assert_match(/foo=nil/, @b)
+  end
+
   def test_deprecated_instance_variable_proxy
     assert_not_deprecated { @dtc.request.size }