These changes all better align with chrome's event ordering/timing.
There are two big changes. The first is that our internal page_navigated event,
which is kind of our heavy hitter, is sent once the header is received as
opposed to (much later) on document load. The main goal of this internal event
is to trigger the "Page.frameNavigated" CDP event which is meant to happen
once the URL is committed, which _is_ on header response.
To accommodate this earlier trigger, new explicit events for DOMContentLoaded
and load have be added.
This drastically changes the flow of events as things go from:
Start Page Navigation
Response Received
Start Frame Navigation
Response Received
End Frame Navigation
End Page Navigation
context clear + reset
DOMContentLoaded
Loaded
TO:
Start Page Navigation
Response Received
End Page Navigation
context clear + reset
Start Frame Navigation
Response Received
End Frame Navigation
DOMContentLoaded
Loaded
So not only does it remove the nesting, but it ensures that the context are
cleared and reset once the main page's navigation is locked in, and before any
frame is created.
This field was recently added and is used to generate correct frameIds in CDP
messages. They remain the same during a navigation event, so calling them
page.id might cause surprises since navigation events create new pages, but
retain the original id. Hence, frame_id is more accurate and hopefully less
surprising.
(This is a small cleanup prior to doing some iframe navigation work).
Our BrowsingContext currently supports 1 target. So we have a per-BC target_id.
Previously, our target had 1 "frame" - our page. So we often treated the
targetId as the frameId. But to work with frames, we need page-specific
frameIds and loaderIds.
This tries to clean up our ids (a little). frameIds are now ids derived from
a new incrementing page.id. This page.id has to be passed around (via http
Requests and through notifications) in order to properly generate messages with
a frameId.
Deciding what should be an lp.assert, vs an std.debug.assert, vs a debug-only
assert is a little arbitrary.
debug-only asserts, guarded with an `if (comptime IS_DEBUG)` obviously avoid the
check in release and thus have a performance advantage. We also use them at
library boundaries. If libcurl says it will always emit a header line with a
trailing \r\n, is that really a check we need to do in production? I don't think
so. First, that code path is checked _a lot_ in debug. Second, it feels a bit
like we're testing libcurl (in production!)..why? A debug-only assertion should
be good enough to catch any changes in libcurl.
