Migrated from sinonjs/sinon#607
Originally created by @terinjokes on Thu, 20 Nov 2014 00:47:58 GMT

FakeXMLHttpRequest's send method currently clobbers the "Content-Type" header if set, by removing anything after the first ";" and forcibly appending ";charset=utf-8".

A real XHR object allows sending binary data via TypedArrays, ArrayBuffers, and Blobs. They also correctly form encode when sent with FormData values. As "Content-Type" might have application-specific behavior, blindingly clobbering them makes it difficult for developers to properly test the functionality.