This patch has the following big pieces:
HTTP support in FetchDriver, which requires the principal of the caller to be passed.
Managing worker lifetime when a fetch() call is in progress.
Managing worker lifetime when a Response body is being read.
Using nsIPipe to link network streams to Request/Response body streams.
Using nsIInputStreamPump to convert Request/Response body streams into respective types.
Folded:
Bug 1039846 - Fetch API: Use a pipe to immediately start writing HTTP body data to InternalResponse.
Bug 1039846 - Assert bodystream can be set only once
Bug 1039846 - Add feature when handling fetch responses on workers
Bug 1039846 - Try to retarget http fetch delivery off main thread.
Bug 1039846 - Safely consume body using nsIInputStreamPump on workers and main thread.
Bug 1039846 - Retarget body reading to stream transport service.
