Monkey Raptor

Update
Jan 23, 2015: This issue has been fixed on Chrome 40+.

You need to update your current (older) Chrome to the latest version.

That happened most of the time whenever opening the developer console on Chrome for the first time, after a page had loaded. I reproduced that error message a lot on our other developed web applications or just visiting other websites.
It's pretty misleading actually. Ms. Leading.

The particular error notification doesn't have any "real" error on the page itself or the network resources of the page.

Discussion links at Stack Overflow:

• Bizarre Error in Chrome Developer Console
• Chrome - ERR_CACHE_MISS

According to one of the discussions above, it will be "fixed" for the 40^th version.

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This still appears on Chrome 40+ (Jan 23, 2015).

YouTube, Chrome, and of course, Google teams have been developing lots of lots of avant-garde media (video) streaming and web performance tweaking techniques. This one is a minor glitch I suppose (on Chrome), which I don't know the meaning of these multiple extensions errors. Well, until I read a discussion on Stack Overflow.
It doesn't have any noticeable/visible errors on the video player itself.

Snapshot:
Discussion link at Stack Overflow:

• Chrome YouTube cast_sender.js console error

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Update
Jan 23, 2015: I don't see this error log anymore on Chrome 40+.
Neat!

This error message (sometimes) happened when I opened the console (for a long time), while typing JavaScript lines then reload a page I was on. But sometimes, it just appeared for no raisin. Thus, reproducing it is kinda 50-50.

Discussion link at Stack Overflow:

• Error shows “Failed to get text for stylesheet (#): No style sheet with given id found”, what does this mean?

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Thank you Chrome developers!
Updated Jan 23, 2015