It is possible to talk to Chrome PDF Viewer(mhjfbmdgcfjbbpaeojofohoefgiehjai) from user-created extensions?

[Brook Hong]

I found there is a function named handleScriptingMessage in chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai/pdf.js, but it only handles four messages 'getAccessibilityJSON'/'getSelectedText'/'print'/'selectAll'. It would be helpful if it handles sendKeyEvent too.

Why I need this?

I created an extension -- Surfingkeys(https://chrome.google.com/webstore/detail/surfingkeys/gfbliohnnapiefjpjlpjnehglfpaknnc) to control the web browser with keyboard, which works for html pages. But I'd like it works for pdf docs in the browser too.