In T191532#4575809 @Ryasmeen noticed that it's possible for PageIssues events to be sent without ReadingDepth
== Background
ReadingDepth events are only set if sendBeacon is available.
If sendBeacon is not available, PageIssues events can still be sent (using the fallback method)
= Developer notes
Strangely I@jdlrobson can replicate this in Safari 11.1.1 (which is strange because according to release notes and [[https://caniuse.com/#feat=beacon |Caniuse]] it should support sendBeacon)
{F25779770}
Is this a problem?On the other hand, we see lots of other Safari 11.1.x clients sending ReadingDepth events (T204143#4578937).
If notThis is a problem because the instrumentation fails to work for browsers where we expected it to work (based on known sendBeacon support). We need to understand which browsers send ReadingDepth data reliably, which will enable us to limit the part of the page issues analysis that relies on ReadinDepth data to those browsers.
Proposal by @jdlrobson:
...we can address this by limiting PageIssues logging to when sendBeacon is available.
Right now we do this:
```
turnOnPageIssuesSchema();
if ( navigator.sendBeacon !== undefined ) {
turnOnReadingDepthSchema();
}
```
but we could do
```
if ( navigator.sendBeacon !== undefined ) {
turnOnPageIssuesSchema();
turnOnReadingDepthSchema();
}
```
~~Update: @tbayer doesn't seem to think this is a problem so we do not need to do anything, but he would like to understand the Safari issue a bit more.~~ This appears to have been a misunderstanding
= Acceptance criteria
[] If navigator.sendBeacon is undefined do not enable Schema:PageIssues