I support an app where we need to be able to preserve the user's rough
scroll position when re-opening a document. It's not enough to keep
track of that offset: we keep track of the pos and both focus the
document and scroll you to it once the view exists.

For some time, we've needed to add a 50ms delay before calling
`tr.scrollIntoView()`. This patch to the demo app simulates it,
scrolling to the text at the bottom of the editor:

``
diff --git a/demo/demo.css b/demo/demo.css
index 06bfe78..813bf22 100644
--- a/demo/demo.css
+++ b/demo/demo.css
@@ -17,6 +17,8 @@ textarea {

 .full {
   max-width: 50em;
+  height: 300px;
+  overflow-y: auto;
 }

 .marked {
diff --git a/demo/demo.ts b/demo/demo.ts
index 48e2c34..80632ec 100644
--- a/demo/demo.ts
+++ b/demo/demo.ts
@@ -1,6 +1,6 @@
 import {Schema, DOMParser} from "prosemirror-model"
 import {EditorView} from "prosemirror-view"
-import {EditorState} from "prosemirror-state"
+import {EditorState, TextSelection} from "prosemirror-state"
 import {schema} from "prosemirror-schema-basic"
 import {addListNodes} from "prosemirror-schema-list"
 import {exampleSetup} from "prosemirror-example-setup"
@@ -10,7 +10,13 @@ const demoSchema = new Schema({
   marks: schema.spec.marks
 })

-let state = EditorState.create({doc: DOMParser.fromSchema(demoSchema).parse(document.querySelector("#content")!),
-                                plugins: exampleSetup({schema: demoSchema})})
+const doc = DOMParser.fromSchema(demoSchema).parse(document.querySelector("#content")!)
+const state = EditorState.create({
+  doc,
+  selection: TextSelection.atEnd(doc),
+  plugins: exampleSetup({schema: demoSchema})
+})

-;(window as any).view = new EditorView(document.querySelector(".full"), {state})
+const view = new EditorView(document.querySelector(".full"), {state})
+view.dispatch(view.state.tr.scrollIntoView())
+;(window as any).view = view
diff --git a/demo/index.html b/demo/index.html
index 4b76a94..e9ad42c 100644
--- a/demo/index.html
+++ b/demo/index.html
@@ -13,6 +13,7 @@

 <div class="full"></div>

+
 <div id=content style="display: none">
 <h2>Demonstration Text</h2>
```

I tracked this down the other day to #1503. That fix makes sense: you
want to guard against selection in another editor being used as the
starting point for the `scrollRectIntoView` walk. Instead of returning
early though, we should fall back to the dom element of the view that is
handling the scroll. That's what this commit does, allowing the scroll
position to be adjusted even if the editor is not yet focused.

Let me know if this patch works for you or if there's a better way to
initialize the view

@@ -239,2 +237,2 @@
-      // Ignore selections outside the editor
-    } else if (this.someProp("handleScrollToSelection", f => f(this))) {
+    let focusNode = this.domSelectionRange().focusNode
+    let startDOM = focusNode && this.dom.contains(focusNode) ? focusNode : this.dom