Use counter submission normally happens at document destruction. For
testing use counters, however, we need to have use counters updated in
telemetry at deterministic points. Therefore, we provide a method on
nsIDOMWindowUtils that forces use counters out to telemetry so we can
examine them.
This patch gives ns{I,}Document the ability to track use counters and
also to send those to telemetry at document destruction time. We push
things to telemetry lazily because we're can't definitively say whether
something has been used until the document is torn down.
This alters nsIWebBrowserPersistable so that startPersistence takes an
outerWindowID. This allows us to target a particular subframe from
beneath an nsFrameLoader, which is useful when attempting to Save
Frame As a remote browser.
--HG--
extra : commitid : KWck2rfRjXw
extra : rebase_source : d2390a8cf1b830e4e1c0fa52574455fbc0b05c14
This is motivated by three separate but related problems:
1. Our concept of recursion depth is broken for things that run from AfterProcessNextEvent observers (e.g. Promises). We decrement the recursionDepth counter before firing observers, so a Promise callback running at the lowest event loop depth has a recursion depth of 0 (whereas a regular nsIRunnable would be 1). This is a problem because it's impossible to distinguish a Promise running after a sync XHR's onreadystatechange handler from a top-level event (since the former runs with depth 2 - 1 = 1, and the latter runs with just 1).
2. The nsIThreadObserver mechanism that is used by a lot of code to run "after" the current event is a poor fit for anything that runs script. First, the order the observers fire in is the order they were added, not anything fixed by spec. Additionally, running script can cause the event loop to spin, which is a big source of pain here (bholley has some nasty bug caused by this).
3. We run Promises from different points in the code for workers and main thread. The latter runs from XPConnect's nsIThreadObserver callbacks, while the former runs from a hardcoded call to run Promises in the worker event loop. What workers do is particularly problematic because it means we can't get the right recursion depth no matter what we do to nsThread.
The solve this, this patch does the following:
1. Consolidate some handling of microtasks and all handling of stable state from appshell and WorkerPrivate into CycleCollectedJSRuntime.
2. Make the recursionDepth counter only available to CycleCollectedJSRuntime (and its consumers) and remove it from the nsIThreadInternal and nsIThreadObserver APIs.
3. Adjust the recursionDepth counter so that microtasks run with the recursionDepth of the task they are associated with.
4. Introduce the concept of metastable state to replace appshell's RunBeforeNextEvent. Metastable state is reached after every microtask or task is completed. This provides the semantics that bent and I want for IndexedDB, where transactions autocommit at the end of a microtask and do not "spill" from one microtask into a subsequent microtask. This differs from appshell's RunBeforeNextEvent in two ways:
a) It fires between microtasks, which was the motivation for starting this.
b) It no longer ensures that we're at the same event loop depth in the native event queue. bent decided we don't care about this.
5. Reorder stable state to happen after microtasks such as Promises, per HTML. Right now we call the regular thread observers, including appshell, before the main thread observer (XPConnect), so stable state tasks happen before microtasks.
William Chen
Kartikaya Gupta
Nathan Froyd
Cameron McCormack
Ryan VanderMeulen
Andrew Osmond
Wes Kocher
Boris Chiou
Ben Tian
Robert Longson
Aryeh Gregor
Brad Lassey
Ehsan Akhgari
Daniel Holbert
Matt Woodrow
Mike Conley
Andrea Marchesini
Francois Marier
Tom Tromey
Hiroyuki Ikezoe
Arnaud Bienner
Benoit Girard
Christoph Kerschbaumer
Kyle Machulis
Terrence Cole
Kyle Huey