NS_AsyncCopy aborts if it receives an NS_BASE_STREAM_WOULD_BLOCK error result
during copying and it is unable to QI the source stream to an
nsIAsyncInputStream. IPCBlobInputStream can return this, especially if it's:
- A freshly created aggregate stream as part of form submission of a type=file
where the Blob will come from the parent because of the file picker but the
stream is being uploaded from the child.
- A ServiceWorker is involved, causing
HttpBaseChannel::EnsureUploadStreamIsCloneable to trigger an NS_AsyncCopy
very early in the process.
IPCBlobInputStream implements nsIAsyncInputStream, and nsMultiplexInputStream
does too (conditionally based on its child streams; if any are async, it takes
step to uniformly expose async behavior). However, due to lack of sufficient
test coverage, nsMIMEInputStream did not get fixed as part of bug 1361443 when
nsMultiplexInputStream gained its nsIAsyncInputStream powers. We address that
here in the same fashion.
Part 1 of this series addresses the test coverage issue.
Slightly less than half (93 / 210) of the NS_METHOD instances in the codebase
are because of the use of NS_CALLBACK in
nsI{Input,Output,UnicharInput},Stream.idl. The use of __stdcall on Win32 isn't
important for these callbacks because they are only used as arguments to
[noscript] methods.
This patch converts them to vanilla |nsresult| functions. It increases the size
of xul.dll by about ~600 bytes, which is about 0.001%.
