Add pausing execution of worklets and dedicated workers

The lifecycle of workers and worklets was undefined in the specification.
Add some formalization around dedicated workers and worklets. Still to
be determined is what happens with shared workers and service workers.

Author: dtapuska

spec.bs

@@ -32,10 +32,17 @@ spec: HTML; urlPrefix: https://html.spec.whatwg.org/multipage/;
     type: dfn; text: media elements; url: media.html#media-element
     type: dfn; text: media pause; url: media.html#internal-pause-steps
     type: dfn; text: media play; url: media.html#internal-play-steps
+    type: dfn; text: dedicated worker agent; url: webappapis.html#dedicated-worker-agent
+    type: dfn; text: worklet agent; url: webappapis.html#worklet-agent
 spec: CSS2; urlPrefix: https://www.w3.org/TR/CSS2/
     type: dfn; text: viewport; url: visuren.html#viewport
 spec: IntersectionObserver; urlPrefix: https://w3c.github.io/IntersectionObserver/
     type: dfn; text: compute the intersection of a target element and the root; url: #calculate-intersection-rect-algo
+spec: ECMA262; urlPrefix: https://tc39.github.io/ecma262/;
+    type: dfn; text: blocked; url: #sec-forward-progress
+    type: dfn; text: realm; url: #sec-code-realms
+spec: CSS-Houdini; urlPrefix: https://drafts.css-houdini.org/worklets;
+    type: dfn; text: owning document; for: worklet; url: #workletglobalscope-owner-document
 </pre>
 
 
@@ -179,6 +186,23 @@ If these conditions aren't met, the document will be in the [=/unfrozen=] state.
 Processing model {#sec-processing-model}
 ========================================
 
+Modifications to worklet and worker behavior {#worklets-workers}
+----------------------------------------------------------------
+
+Any [=worklet agent=] whose single [=/realm=]'s [=Realm/global object=]'s [=worklet/owning document=] is [=/frozen=] must become [=blocked=].
+Any [=dedicated worker agent=] whose single [=/realm=]'s [=Realm/global object=]'s [=DedicatedWorkerGlobalScope/owning document=] is non-null and [=/frozen=] must become [=blocked=].
+
+<div algorithm>
+    To determine the <dfn for="DedicatedWorkerGlobalScope" export>owning document</dfn> for a {{DedicatedWorkerGlobalScope}} |workerGlobalScope|:
+
+    1. If |workerGlobalScope|'s [=owner set=] consists of a single {{Document}} |document|, then return |document|.
+    1. If |workerGlobalScope|'s [=owner set=] consists of a single {{DedicatedWorkerGlobalScope}} |parentWorkerGlobalScope|, then return |parentWorkerGlobalScope|'s [=owning document=].
+    1. Return null.
+
+    NOTE: A {{DedicatedWorkerGlobalScope}}'s [=owner set=] will always have exactly one item.
+</div>
+
+
 Modifications to the HTML Standard {#mod}
 --------------------------------------------