Fix RepeatedField#delete_if (#4292)

Make RepeatedField#delete_if consistent with Array#delete_if.

ruby/lib/google/protobuf/repeated_field.rb

@@ -150,12 +150,12 @@ module Google
       end
 
 
-      %w(delete delete_at delete_if shift slice! unshift).each do |method_name|
+      %w(delete delete_at shift slice! unshift).each do |method_name|
         define_array_wrapper_method(method_name)
       end
 
 
-      %w(collect! compact! fill flatten! insert reverse!
+      %w(collect! compact! delete_if fill flatten! insert reverse!
         rotate! select! shuffle! sort! sort_by! uniq!).each do |method_name|
         define_array_wrapper_with_result_method(method_name)
       end

ruby/tests/repeated_field_test.rb

@@ -369,6 +369,15 @@ class RepeatedFieldTest < Test::Unit::TestCase
     end
   end
 
+  def test_delete_if
+    m = TestMessage.new
+    reference_arr = %w(foo bar baz)
+    m.repeated_string += reference_arr.clone
+    check_self_modifying_method(m.repeated_string, reference_arr) do |arr|
+      arr.delete_if { |v| v == "bar" }
+    end
+  end
+
   def test_fill
     m = TestMessage.new
     reference_arr = %w(foo bar baz)