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Move ScreenOrientationProvider and ScreenOrientationDispatcherHost from content/browser/screen_orientation/ to content/public/browser/ to expose them to other libraries. This will allow Ash to use them to implement the ScreenOrientationProvider on Chrome OS. Created an implementation of ScreenOrientationDispatcherHost.
BUG=396760

Review URL: https://codereview.chromium.org/508603003

Cr-Commit-Position: refs/heads/master@{#294819}