We currently store Web::Fetch::Infrastructure::Response objects in the
HTTP cache. They are associated with their original realm, but when we
use a cached response, we clone it into the target realm. For example,
two <iframe> objects loading the same HTML will be in different realms.
When we clone the response, we must use the target realm throughout the
entire cloning process. We neglected to do this for the cloned response
body stream, which is cloned via teeing. The result was the the stream
for the "cloned" response was created in the original realm, causing
issues down the line when reading from that stream tried to handle read
promises on behalf of the original realm. There are protections in place
to prevent this from happening, and the cached response read would never
complete.
This mistakenly implemented the 'piped to' operation on ReadableStream.
No functional difference as the caller was doing the extra work already
of 'piped through' vs 'piped to'.
As far as I can tell there is no change in WPT from this implementation.
But these steps should be more effecient than using the non BYOB steps
as we can make direct use of the provided buffer to the byte stream.
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
