Remove unsused output_method argument

Fixes Ruby Bug 9876.

lib/irb.rb

@@ -441,8 +441,8 @@ module IRB
     # parsed as a :method_add_arg and the output won't be suppressed
 
     # Creates a new irb session
-    def initialize(workspace = nil, input_method = nil, output_method = nil)
-      @context = Context.new(self, workspace, input_method, output_method)
+    def initialize(workspace = nil, input_method = nil)
+      @context = Context.new(self, workspace, input_method)
       @context.main.extend ExtendCommandBundle
       @signal_status = :IN_IRB
       @scanner = RubyLex.new

lib/irb/context.rb

@@ -25,7 +25,7 @@ module IRB
     # +nil+::     uses stdin or Reidline or Readline
     # +String+::  uses a File
     # +other+::   uses this as InputMethod
-    def initialize(irb, workspace = nil, input_method = nil, output_method = nil)
+    def initialize(irb, workspace = nil, input_method = nil)
       @irb = irb
       if workspace
         @workspace = workspace
@@ -111,12 +111,6 @@ module IRB
       end
       self.save_history = IRB.conf[:SAVE_HISTORY] if IRB.conf[:SAVE_HISTORY]
 
-      if output_method
-        @output_method = output_method
-      else
-        @output_method = StdioOutputMethod.new
-      end
-
       @echo = IRB.conf[:ECHO]
       if @echo.nil?
         @echo = true