1351062 - [e10s] mouse movements are captured in a wrong way if CSS 'transform' changes in iframe

Status: NEW

(Core :: Layout, defect, P3)

Description

[684sigma]

Attachment: mouse movements are captured in a wrong way if transform changes, by reporter.html

I have a problem with Firefox Beta 52. It also happens in Beta 53, Nightly 55. Doesn't happen in ESR 45.
On some sites I noticed a very weird behavior: mouse movements are captured incorrectly, as if mouse cursor was placed in a different area. I experimented a bit, and created a working example of the bug.
I'll check those sites once this bug is fixed. Here's how to reproduce the bug:

1. Open attached page
2. Click on the button, then immediately move mouse over iframe
3. Keep moving mouse up and down within iframe and right-clicking, but don't click on buttons.

Result: buttons become hovered far away from mouse cursor; context menu appears far away from mouse cursor.
Expected: normal behavior.

I've added "[e10s]" in the summary, because it isn't reproducible if in Nightlly I disable "multiprocess".
Please correct me if this logic is incorrect.

Comment 1

[684sigma]

Another bug detected with that page is bug 1351063.

Comment 2

[Loic]

I found a regression range in FF42:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=b0b3dcfa5557&tochange=d3228c82badd

I think it's a side-effect of bug 1172239 with e10s enabled.

Comment 3

[Andrew Overholt [:overholt]]

I'm hoping this is more of a Layout thing :)

Comment 4

[Liz Henry (:lizzard) (relman/hg->git project)]

Too late for a fix for 53, fix-optional for 54, minor carryover regression.

Comment 5

[Mike Taylor [:miketaylr]]

Astley, should this be fix-optional for 57?

Comment 6

[Astley Chen (inactive)]

Attachment: iframe.html

Extracted iframe content to a separate HTML file.

Comment 7

[Astley Chen (inactive)]

Attachment: Refreshed-test-case.html

Refresh the test case as iframe with src attribute in data URI format will be taken as unique, opaque origins. See bug 1324406.