* fix: update and enable osr
* fix: update MacHelper view to call GetNativeView
* style: move stuff around to make more sense
* chore: move OSR related things in SetOwnerWindow to CommonWebContentsDelegate
* fix: avoid crashing when GetOffscreenRenderWidgetHostView is called
* fix: specify default for current_device_scale_factor_
* build: define compile time features with buildflag header
* refactor: switch to BUILDFLAG(ENABLE_DESKTOP_CAPTURER)
* refactor: switch to BUILDFLAG(ENABLE_RUN_AS_NODE)
* refactor: switch to BUILDFLAG(ENABLE_OSR)
* refactor: switch to BUILDFLAG(ENABLE_VIEW_API)
* refactor: switch to BUILDFLAG(ENABLE_PEPPER_FLASH)
* refactor: switch to BUILDFLAG(OVERRIDE_LOCATION_PROVIDER)
* refactor: switch to BUILDFLAG(ENABLE_PDF_VIEWER)