merge revision(s) 0300ea5a6c8a7a49feed73318fc8a991aa89fcfc:

	[ruby/net-http] Improve performance of HTTPHeader#content_type

	In the existing implementation, `main_type` and `sub_type` would end up
	being called multiple times potentially.

	Instead of doing that, save the result so it can be re-used.

	https://github.com/ruby/net-http/commit/179976f7ea
	---
	 lib/net/http/header.rb | 12 ++++++++----
	 1 file changed, 8 insertions(+), 4 deletions(-)

1 files changed, 8 insertions, 4 deletions

diff --git a/lib/net/http/header.rb b/lib/net/http/header.rb
index b704860c90..ec5552f04d 100644
--- a/lib/net/http/header.rb
+++ b/lib/net/http/header.rb
@@ -699,10 +699,14 @@ module Net::HTTPHeader
   #   res.content_type    # => "application/json"
   #
   def content_type
-    return nil unless main_type()
-    if sub_type()
-    then "#{main_type()}/#{sub_type()}"
-    else main_type()
+    main = main_type()
+    return nil unless main
+
+    sub = sub_type()
+    if sub
+      "#{main}/#{sub}"
+    else
+      main
     end
   end