cc: Return whether any layer was scrolled from InputHandlerClient::scrollBy.

cc: Return whether any layer was scrolled from InputHandlerClient::scrollBy.

BUG=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=167721

[sadrul, 2012-11-13 23:24:21]

Hi! The compositor thread currently eats the scroll events ('scroll events' ==
'mouse wheel' or 'gesture update events', and 'eats' == 'claims to have handled
the event') even when nothing was actually scrolled. This needs to be fixed to
allow overscroll history navigation.

To fix this, it is necessary to know whether anything was in fact scrolled. This
patch does that.

The next part is to mark the event as unprocessed. The patch for that is here:
http://codereview.chromium.org/11369231/

Dana, would you please review and let me know if the patches are doing the right
things? If the changes look reasonable, I will look into adding tests and put up
CL(s) for formal review (i.e. in webkit bugzilla for the webkit patch, and I
suppose some two/three-sided patch so things continue to work as the scrollBy
API changes)

Rob, if you get a chance to try this out on mac and see if the current
overscroll stuff works there, that would be awesome! (I promise I will get a mac
build going some time tomorrow)

[danakj, 2012-11-14 02:44:22]

Hey Sadrul,

This all seems pretty reasonable to me. You might wanna ask jamesr@ also as he
owns the API.

http://codereview.chromium.org/11365238/diff/1/cc/layer_tree_host_impl.cc
File cc/layer_tree_host_impl.cc (right):

http://codereview.chromium.org/11365238/diff/1/cc/layer_tree_host_impl.cc#new...
cc/layer_tree_host_impl.cc:1193: return true;
I guess this function eats the whole pendingDelta all the time, so a bool seems
reasonable and you can ignore my other comment.

[sadrul, 2012-11-14 17:02:04]

Thanks Dana!

+jamesr

I will put up a corresponding webkit patch shortly.

[sadrul, 2012-11-14 18:06:20]

On 2012/11/14 17:02:04, sadrul wrote:
> Thanks Dana!
> 
> +jamesr
> 
> I will put up a corresponding webkit patch shortly.

The webkit patch is up at: https://bugs.webkit.org/show_bug.cgi?id=102246

[jamesr, 2012-11-14 18:11:33]

lgtm