[IntersectionObserver] Enable observations across shadow DOM roots.

third_party/WebKit/LayoutTests/intersection-observer/shadow-content-expected.txt

Index: third_party/WebKit/LayoutTests/intersection-observer/shadow-content-expected.txt
diff --git a/third_party/WebKit/LayoutTests/intersection-observer/shadow-content-expected.txt b/third_party/WebKit/LayoutTests/intersection-observer/shadow-content-expected.txt
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index 0000000000000000000000000000000000000000..3cc151964f52fac334508f84cde4a076f695b9d8
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+++ b/third_party/WebKit/LayoutTests/intersection-observer/shadow-content-expected.txt
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+Tests that observations can be made across shadow DOM boundaries.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS entries.length is 0
+PASS entries.length is 1
+PASS entries[0].boundingClientRect.left is 8
+PASS entries[0].boundingClientRect.right is 108
+PASS entries[0].boundingClientRect.top is 8
+PASS entries[0].boundingClientRect.bottom is 108
+PASS entries[0].intersectionRect.left is 8
+PASS entries[0].intersectionRect.right is 108
+PASS entries[0].intersectionRect.top is 8
+PASS entries[0].intersectionRect.bottom is 108
+PASS entries[0].rootBounds.left is 0
+PASS entries[0].rootBounds.right is 800
+PASS entries[0].rootBounds.top is 0
+PASS entries[0].rootBounds.bottom is 600
+PASS entries[0].target is [object HTMLDivElement]
+PASS successfullyParsed is true
+
+TEST COMPLETE
+