Screen overridings are fixed

Several tests override display::Screen and they left a screen
overridden after execution. When next test from current batch is
executed and it uses display::Screen::GetScreen(), it gets broken
screen.
This CL based on
https://chromium-review.googlesource.com/c/chromium/src/+/963961

Bug: None
Change-Id: I098c96a024a4817abaaf735563d5bddd93c461d8
Reviewed-on: https://chromium-review.googlesource.com/974142
Commit-Queue: Ken Rockot <rockot@chromium.org>
Reviewed-by: Ken Rockot <rockot@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548485}

• chrome/browser/extensions/api/tabs/tabs_api_unittest.cc[diff]
• chrome/browser/extensions/extension_context_menu_model_unittest.cc[diff]
• device/BUILD.gn[diff]
• device/vr/orientation/orientation_device_unittest.cc[diff]
• extensions/browser/BUILD.gn[diff]
• extensions/browser/api/system_display/system_display_apitest.cc[diff]
• ui/display/BUILD.gn[diff]
• ui/display/test/scoped_screen_override.cc[Added - diff]
• ui/display/test/scoped_screen_override.h[Added - diff]