Report tag_name as ShadowRoot for shadow roots (#318)

Author: myabc

lib/capybara/cuprite/node.rb

@@ -139,7 +139,7 @@ def unselect_option
       end
 
       def tag_name
-        @tag_name ||= description["nodeName"].downcase
+        @tag_name ||= description["shadowRootType"] ? "ShadowRoot" : description["nodeName"].downcase
       end
 
       def visible?

spec/features/session_spec.rb

@@ -452,7 +452,7 @@
         shadow_root = @session.find(:css, "#shadow_host").shadow_root
         expect do
           expect(shadow_root).to have_css("#shadow_content", text: "Not in the document")
-        end.to raise_error(/tag="#document-fragment"/)
+        end.to raise_error(/tag="ShadowRoot"/)
       end
 
       it "extends visibility check across shadow host boundary" do

spec/spec_helper.rb

@@ -59,7 +59,6 @@ module TestSessions
       node #visible? details non-summary descendants should be non-visible
       node #visible? works when details is toggled open and closed
       node #set should submit single text input forms if ended with
-      node #shadow_root should produce error messages when failing
       #has_field with valid should be false if field is invalid
       #has_element? should be true if the given element is on the page
       #assert_matches_style should raise error if the elements style doesn't contain the given properties