Add initial Blink-side support for the Screen Orientation API

LayoutTests/screen_orientation/screenorientation-api-expected.txt

Index: LayoutTests/screen_orientation/screenorientation-api-expected.txt
diff --git a/LayoutTests/screen_orientation/screenorientation-api-expected.txt b/LayoutTests/screen_orientation/screenorientation-api-expected.txt
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+++ b/LayoutTests/screen_orientation/screenorientation-api-expected.txt
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+Validates the Screen Orientation API is exposed.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS screen.lockOrientation is defined.
+PASS screen.unlockOrientation is defined.
+PASS screen.orientation is defined.
+PASS screen.onorientationchange is defined.
+PASS screen.__proto__.__proto__ is EventTarget.prototype
+PASS screen.addEventListener is defined.
+PASS screen.removeEventListener is defined.
+PASS screen.dispatchEvent is defined.
+PASS successfullyParsed is true
+
+TEST COMPLETE
+