[css-view-transitions-2] Apply feedback from F2F

- Disable view-transitions for reload
- Add wording in security about 3p CSS
- Fire reveal event before rAF, inside update the rendering

Closes w3c#8784
Closes w3c#8889
See w3c#8048

css-view-transitions-2/Overview.bs

@@ -36,6 +36,7 @@ spec:css-view-transitions-1;
 spec:dom; type:dfn; text:document
 spec:css22; type:dfn; text:element
 spec:html
+	text: current session history entry; type: dfn;
 	text: latest entry; type: dfn;
 	text: was created via cross-origin redirects; type: dfn;
 	text: run the animation frame callbacks; type: dfn;
@@ -291,7 +292,7 @@ The <dfn attribute for=PageRevealEvent>viewTransition</dfn> [=getter steps=] are
 		Prepend a step at the beginning of the task [=queue a global task|queued=] on |navigable|'s [=active window=]
 		when <a href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#apply-the-history-step">applying the history step</a> (14.11.1, <a href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#updating-the-traversable:queue-a-global-task-3">here</a>):
 
-		If |changingNavigationContinuation| update-only is false, then [=setup outbound cross-document view transition=] given |oldDocument|, |newDocument| and the remaining steps and return from these steps.
+		If |changingNavigationContinuation| update-only is false and |targetEntry| is not |navigable|'s [=current session history entry=], then [=setup outbound cross-document view transition=] given |oldDocument|, |newDocument| and the remaining steps and return from these steps.
 
 		Note: This would wait until a transition is captured or skipped before proceeding to unloading the old document and activating the new one.
 	</div>