[Replacements] Fix duration when replacing gif -> webm

app/logical/upload_service/replacer.rb

@@ -82,6 +82,7 @@ class UploadService
         post.image_width = upload.image_width
         post.image_height = upload.image_height
         post.file_size = upload.file_size
+        post.duration = upload.video_duration(upload.file.path)
         post.source = "#{replacement.source}\n" + post.source
         post.tag_string = upload.tag_string
         # Reset ownership information on post.

test/unit/post_replacement_test.rb

@@ -146,7 +146,6 @@ class PostReplacementTest < ActiveSupport::TestCase
       end
     end
 
-
     should "update post with new image" do
       old_md5 = @post.md5
       @replacement.approve! penalize_current_uploader: true
@@ -249,6 +248,18 @@ class PostReplacementTest < ActiveSupport::TestCase
       @replacement.approve! penalize_current_uploader: false
       assert_equal ["Status must be pending or original to approve"], @replacement.errors.full_messages
     end
+
+    context "update the duration" do
+      setup do
+        @replacement = FactoryBot.create(:webm_replacement, creator: @user, creator_ip_addr: '127.0.0.1', post: @post)
+      end
+
+      should "when the replacement is a video" do
+        @replacement.approve! penalize_current_uploader: false
+        @post.reload
+        assert @post.duration
+      end
+    end
   end
 
   context "Toggle:" do