Remove hard require to ActionView from ActionMailer

actionmailer/lib/action_mailer.rb

@@ -22,7 +22,6 @@
 #++
 
 require 'abstract_controller'
-require 'action_view'
 require 'action_mailer/version'
 
 # Common Active Support usage in Action Mailer

actionmailer/lib/action_mailer/base.rb

@@ -1,5 +1,4 @@
 require 'mail'
-require 'action_view/base'
 require 'action_mailer/collector'
 require 'active_support/core_ext/string/inflections'
 require 'active_support/core_ext/hash/except'

actionmailer/test/abstract_unit.rb

@@ -14,6 +14,7 @@ require 'action_mailer/test_case'
 require 'mail'
 
 # Emulate AV railtie
+require 'action_view'
 ActionMailer::Base.send(:include, ActionView::Layouts)
 
 # Show backtraces for deprecated behavior for quicker cleanup.