Add initial Blink-side support for the Screen Orientation API

LayoutTests/screen_orientation/locking-fires-event-expected.txt

Index: LayoutTests/screen_orientation/locking-fires-event-expected.txt
diff --git a/LayoutTests/screen_orientation/locking-fires-event-expected.txt b/LayoutTests/screen_orientation/locking-fires-event-expected.txt
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+Validates that screen.lockOrientation() fires an event if the orientation had to be changed to meet the locking requirements.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS screen.orientation is "portrait-primary"
+locking orientation to 'landscape-primary'.
+PASS screen.lockOrientation('landscape-primary') is true
+PASS screen.orientation is "portrait-primary"
+Received an 'orientationchange' event.
+PASS orientationChangeEventCount is 1
+PASS testEvent.type is "orientationchange"
+PASS screen.orientation is "landscape-primary"
+PASS successfullyParsed is true
+
+TEST COMPLETE
+