Bug 1044224 - [Messages][Tests] Generate assets on the fly instead of loading it with XHR. Generating assets using canvas. r=julien

the only problem here is that this image was made to be larger than 300KB, while your generated image is not.

I've no issue with this as long as you change the max mms size (in MockSettings, I guess) to less than your generated image size in the related tests.