* refactor: clean up webFrame implementation to use gin wrappers
The previous implementation of webFrame in the renderer process leaked
sub-frame contexts and global objects across the context boundaries thus
making it possible for apps to either maliciously or accidentally
violate the contextIsolation boundary.
This re-implementation binds all methods in native code directly to
content::RenderFrame instances instead of relying on JS to provide a
"window" with every method request. This is much more consistent with
the rest of the Electron codebase and is substantially safer.
* chore: un-re-order for ease of review
* chore: pass isolate around instead of ErrorThrower
* chore: fix rebase typo
* chore: remove unused variables
