PPAPISharedImagesForVideoDecoderAllowed

This policy controls the recent refactor for VideoDecoder APIs in PPAPI plugin. The migration only affects internal implementation details and should not change any behavior. However, this policy can be used in case any PPAPI applications do not work as expected. When the policy is left unset or set to Enabled, the browser will decide which implementation is used. When the policy is set to Disabled, browser will use the old implementation until the policy is expired. NOTE: Only newly-started renderer processes will reflect changes to this policy while the browser is running.