* spec: clean up after a failed window count assertion
Previously when this assertion failed all tests that ran after the
failed assertion also failed. This ensure that the assertion fails for
the test that actually caused the issue but cleans up the left-over
windows so that future tests do not fail.
* fix: maintain a ref count for objects sent over remote
Previously there was a race condition where a GC could occur in the
renderer process between the main process sending a meta.id and the
renderer pulling the proxy out its weakmap to stop it being GC'ed.
This fixes that race condition by maintaining a "sent" ref count in the
object registry and a "received" ref count in the object cache on the
renderer side. The deref request now sends the number of refs the
renderer thinks it owns, if the number does not match the value in the
object registry it is assumed that there is an IPC message containing a
new reference in flight and this race condition was hit.
The browser side ref count is then reduced and we wait for the new deref
message. This guaruntees that an object will only be removed from the
registry if every reference we sent has been guarunteed to be unreffed.
After the page does navigations, garbage collection can still happen in
the old context. This commit changes to store references to remote objects
by _pages_, instead of by _WebContents_.
Previously we rely on the v8util.setDestructor to dereference the remote
objects in JavaScript, however as documented in V8, it is forbidden to
call V8 APIs in object's destructor (e.g. the weak callback), and doing
so would result in crashs.
This commit removes the JavaScript setDestructor method, and avoids
doing the dereference work with V8.
