Implement ShadowRoot.delegatesFocus 4/4 (match CSS :focus for shadow host)

LayoutTests/fast/dom/shadow/focus-with-dom-mutation-expected.txt

Index: LayoutTests/fast/dom/shadow/focus-with-dom-mutation-expected.txt
diff --git a/LayoutTests/fast/dom/shadow/focus-with-dom-mutation-expected.txt b/LayoutTests/fast/dom/shadow/focus-with-dom-mutation-expected.txt
new file mode 100644
index 0000000000000000000000000000000000000000..ff866d6e36010f2e91ba57258e1a591e2d107c07
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+++ b/LayoutTests/fast/dom/shadow/focus-with-dom-mutation-expected.txt
@@ -0,0 +1,19 @@
+Test if :focus matching state of shadow host is properly handled in case of DOM mutation.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+(1/2) DOM mutation across shadow boundary with delegatesFocus=false
+PASS backgroundColorOf('host') is "rgb(255, 255, 255)"
+PASS backgroundColorOf('host') is "rgb(255, 255, 255)"
+PASS backgroundColorOf('host') is "rgb(255, 255, 255)"
+PASS backgroundColorOf('host') is "rgb(255, 255, 255)"
+(2/2) DOM mutation across shadow boundary with delegatesFocus=true
+PASS backgroundColorOf('host') is "rgb(255, 255, 255)"
+PASS backgroundColorOf('host') is "rgb(0, 128, 0)"
+PASS backgroundColorOf('host') is "rgb(255, 255, 255)"
+PASS backgroundColorOf('host') is "rgb(255, 255, 255)"
+PASS successfullyParsed is true
+
+TEST COMPLETE
+