MD Settings: in cr_dialog, prevent intersectionObserver from firing early.

ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js

Index: ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
diff --git a/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js b/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
index c98c75ac4053eda397cdc7758103f9edb91fd87d..d4229154365610c144d1f56d8cf381fa6ada2846 100644
--- a/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
+++ b/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
@@ -89,8 +89,12 @@ Polymer({
             root: bodyContainer,
             threshold: 0,
           }));
-      this.intersectionObserver_.observe(bottomMarker);
-      this.intersectionObserver_.observe(topMarker);
+
+      // Make sure the handler isn't triggered before the dialog is rendered.
+      Polymer.RenderStatus.afterNextRender(this, function() {

[dpapad, 2017/04/12 01:05:51]

Should we be calling observe() in ready() instead? According to the docs
"Called after property values are set and local DOM is initialized."

[Dan Beam, 2017/04/12 01:07:13]

i'm fairly sure that attached() happens after ready().

[scottchen, 2017/04/12 01:43:05]

Yep, attached() fires after ready(). Not sure if it's due to how dialog gets
rendered, but apparently when attached() gets called, only the overlay is
visible, the actual modal is not yet.

+        this.intersectionObserver_.observe(bottomMarker);
+        this.intersectionObserver_.observe(topMarker);
+      });
     }
   },