Implement a Hit Test Cache.

LayoutTests/fast/events/hit-test-cache-expected.txt

Index: LayoutTests/fast/events/hit-test-cache-expected.txt
diff --git a/LayoutTests/fast/events/hit-test-cache-expected.txt b/LayoutTests/fast/events/hit-test-cache-expected.txt
new file mode 100644
index 0000000000000000000000000000000000000000..a83da6a5f855c5083a86f18789481f332665b3e1
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+++ b/LayoutTests/fast/events/hit-test-cache-expected.txt
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+Ensure hit test cache works in correct scenarios of scrolling, dom and style changes.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS successfullyParsed is true
+
+TEST COMPLETE
+PASS successfullyParsed is true
+
+TEST COMPLETE
+Hit test main div
+---------------------
+PASS document.elementFromPoint(60,60) is internals.elementFromPointNoCache(document, 60, 60)
+PASS hitTestCountDelta() is 2
+PASS hitTestCacheHitsDelta() is 0
+PASS document.elementFromPoint(60,60) is internals.elementFromPointNoCache(document, 60, 60)
+PASS hitTestCountDelta() is 2
+PASS hitTestCacheHitsDelta() is 1
+
+Hit test fixed div after scroll
+---------------------
+PASS document.elementFromPoint(12,12) is internals.elementFromPointNoCache(document, 12, 12)
+PASS hitTestCountDelta() is 2
+PASS hitTestCacheHitsDelta() is 0
+PASS document.elementFromPoint(10,60) is internals.elementFromPointNoCache(document, 10, 60)
+PASS hitTestCountDelta() is 2
+PASS hitTestCacheHitsDelta() is 0
+PASS document.elementFromPoint(12,12) is internals.elementFromPointNoCache(document, 12, 12)
+PASS hitTestCountDelta() is 2
+PASS hitTestCacheHitsDelta() is 0
+
+Hit test after style change
+---------------------
+PASS document.elementFromPoint(12,12) is internals.elementFromPointNoCache(document, 12, 12)
+PASS hitTestCountDelta() is 2
+PASS hitTestCacheHitsDelta() is 0
+PASS document.elementFromPoint(12,12) is internals.elementFromPointNoCache(document, 12, 12)
+PASS hitTestCountDelta() is 2
+PASS hitTestCacheHitsDelta() is 0
+
+Hit test after dom manipulation
+---------------------
+PASS document.elementFromPoint(12,12) is internals.elementFromPointNoCache(document, 12, 12)
+PASS hitTestCountDelta() is 2
+PASS hitTestCacheHitsDelta() is 0
+PASS document.elementFromPoint(12,12) is internals.elementFromPointNoCache(document, 12, 12)
+PASS hitTestCountDelta() is 2
+PASS hitTestCacheHitsDelta() is 0
+PASS successfullyParsed is true
+
+TEST COMPLETE
+