this script is intented to inject the ethereum provider into dapp's page.
Although content-script share the same dom with dapp, but the context is different.
content-script will inject the provider with a inline script element at document_start.
content-script also generate a random value as the broadcastChannel(broadcastChannelMessage.ts) name, to establise channel between content-script and ethereum provider.
when dapp use the provider function, like ethereum.request, the provider will send a message to content-script with broadcastChannel.
the content-script will connect background in the start through runtime.connect().(portMessage.ts)
after content-script receive the message from dapp, it will send the message to background, using the runtime channel.
in a nutshell, the extension can only handle one request at the same time for each page. before the request solved, other requests are queued to send.
the request will be queued in the provider when dapp page's visibility === hidden.