Bugzilla

I've decided to fix bug 1586986 and bug 1586149 altogether in this bug. Otherwise we will introduce undesirable weird behaviors.

There are two caveats with regard to visual viewport size changes;
 1) Firing visual viewport resize events means that any arbitrary scripts can be run in the callback
    so even if we don't explicitly flush position:fixed elements styles AND if we use the up-to-date
    visual viewport size in layout, it's possible that position:fixed elements positions are changed
    by unpredictable scripts. So if we update the visual viewport size in layout, we should also explicitly
    flush positions:fixed elements.

 2) As a result of 1), once position:fixed elements are re-positioned with the up-to-date visual viewport size
    by the flush, 'fixed layer margins' on the compositor which comes from android-components 
    via setVerticalClipping is no longer valid as it is.  We need to _negate_ the value by the _current_
    dynamic toolbar height.

I hope this helps reviewers to review patches here.

I've decided to fix bug 1586147 and bug 1586149 altogether in this bug. Otherwise we will introduce undesirable weird behaviors.

There are two caveats with regard to visual viewport size changes;
 1) Firing visual viewport resize events means that any arbitrary scripts can be run in the callback
    so even if we don't explicitly flush position:fixed elements styles AND if we use the up-to-date
    visual viewport size in layout, it's possible that position:fixed elements positions are changed
    by unpredictable scripts. So if we update the visual viewport size in layout, we should also explicitly
    flush positions:fixed elements.

 2) As a result of 1), once position:fixed elements are re-positioned with the up-to-date visual viewport size
    by the flush, 'fixed layer margins' on the compositor which comes from android-components 
    via setVerticalClipping is no longer valid as it is.  We need to _negate_ the value by the _current_
    dynamic toolbar height.

I hope this helps reviewers to review patches here.