Fix other session icons

[yhtt2020]

thank for your project. when i use browser-action to display extension icons. it can't show in a default-session window. so i added a method called setupProtocol in browser/index.ts public setupProtocol(session:Electron.Session){ this.api.browserAction.setupProtocol(session) } after that i added a public method in api/browser-action.ts such like this public setupProtocol(session:Electron.Session){ return session.protocol.registerBufferProtocol('crx', this.handleCrxRequest) } so ,we can register the protocol in other sessions.

and i also added an api to getCurrentWindow

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