Move Fennec theme files that are common to GeckoView into geckoview.jar,
and place them under chrome://geckoview/. These include content
stylesheets, accessible-caret images, and video-control images. Update
previous URIs to point to the new location.

MozReview-Commit-ID: D8mrDZFnrdZ

--HG--
rename : mobile/android/themes/core/content.css => mobile/android/themes/geckoview/content.css
rename : mobile/android/themes/core/images/accessiblecaret-normal-hdpi.png => mobile/android/themes/geckoview/images/accessiblecaret-normal-hdpi.png
rename : mobile/android/themes/core/images/accessiblecaret-normal-xhdpi.png => mobile/android/themes/geckoview/images/accessiblecaret-normal-xhdpi.png
rename : mobile/android/themes/core/images/accessiblecaret-normal-xxhdpi.png => mobile/android/themes/geckoview/images/accessiblecaret-normal-xxhdpi.png
rename : mobile/android/themes/core/images/accessiblecaret-tilt-left-hdpi.png => mobile/android/themes/geckoview/images/accessiblecaret-tilt-left-hdpi.png
rename : mobile/android/themes/core/images/accessiblecaret-tilt-left-xhdpi.png => mobile/android/themes/geckoview/images/accessiblecaret-tilt-left-xhdpi.png
rename : mobile/android/themes/core/images/accessiblecaret-tilt-left-xxhdpi.png => mobile/android/themes/geckoview/images/accessiblecaret-tilt-left-xxhdpi.png
rename : mobile/android/themes/core/images/accessiblecaret-tilt-right-hdpi.png => mobile/android/themes/geckoview/images/accessiblecaret-tilt-right-hdpi.png
rename : mobile/android/themes/core/images/accessiblecaret-tilt-right-xhdpi.png => mobile/android/themes/geckoview/images/accessiblecaret-tilt-right-xhdpi.png
rename : mobile/android/themes/core/images/accessiblecaret-tilt-right-xxhdpi.png => mobile/android/themes/geckoview/images/accessiblecaret-tilt-right-xxhdpi.png
rename : mobile/android/themes/core/images/dropmarker-right.svg => mobile/android/themes/geckoview/images/dropmarker-right.svg
rename : mobile/android/themes/core/images/dropmarker.svg => mobile/android/themes/geckoview/images/dropmarker.svg
rename : mobile/android/themes/core/images/cast-active.svg => mobile/android/themes/geckoview/images/videocontrols-cast-active.svg
rename : mobile/android/themes/core/images/cast-ready.svg => mobile/android/themes/geckoview/images/videocontrols-cast-ready.svg
rename : mobile/android/themes/core/images/exitfullscreen.svg => mobile/android/themes/geckoview/images/videocontrols-exitfullscreen.svg
rename : mobile/android/themes/core/images/fullscreen.svg => mobile/android/themes/geckoview/images/videocontrols-fullscreen.svg
rename : mobile/android/themes/core/images/mute.svg => mobile/android/themes/geckoview/images/videocontrols-mute.svg
rename : mobile/android/themes/core/images/pause.svg => mobile/android/themes/geckoview/images/videocontrols-pause.svg
rename : mobile/android/themes/core/images/play.svg => mobile/android/themes/geckoview/images/videocontrols-play.svg
rename : mobile/android/themes/core/images/scrubber.svg => mobile/android/themes/geckoview/images/videocontrols-scrubber.svg
rename : mobile/android/themes/core/images/unmute.svg => mobile/android/themes/geckoview/images/videocontrols-unmute.svg
rename : mobile/android/themes/core/scrollbar-apz.css => mobile/android/themes/geckoview/scrollbar-apz.css
rename : mobile/android/themes/core/touchcontrols.css => mobile/android/themes/geckoview/videocontrols.css