Don't transfer viewport to an invalid/dirty <use> instance

Don't transfer viewport to an invalid/dirty <use> instance

If an update is pending for a <use> shadow tree, the width/height
needn't be updated, since the update of the shadow tree will do it.
Make sure to clear the reference to the instance root when
invalidating the shadow tree.
Also split clearResourceReferences into a few different parts.

BUG=516051
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=201738

[fs, 2015-08-31 13:09:43]

fs@opera.com changed reviewers:
+ pdr@chromium.org

[fs, 2015-08-31 13:09:43]

Optionally I guess m_targetElementInstance could be cleared (and the shadow tree
dropped etc) up front when invalidating the shadow tree, but that would be a
slightly more involved fix.

[pdr., 2015-09-01 21:46:57]

On 2015/08/31 at 13:09:43, fs wrote:
> Optionally I guess m_targetElementInstance could be cleared (and the shadow
tree dropped etc) up front when invalidating the shadow tree, but that would be
a slightly more involved fix.

There are many checks for m_targetElementInstance in SVGUseElement.cpp and I
don't see an easy way to say whether one needs to check m_targetElementInstance
or shadowTreeIsValid() in these cases. I think it would be better to clear
m_targetElementInstance.

[fs, 2015-09-03 10:35:56]

On 2015/09/01 21:46:57, pdr wrote:
> On 2015/08/31 at 13:09:43, fs wrote:
> > Optionally I guess m_targetElementInstance could be cleared (and the shadow
> tree dropped etc) up front when invalidating the shadow tree, but that would
be
> a slightly more involved fix.
> 
> There are many checks for m_targetElementInstance in SVGUseElement.cpp and I
> don't see an easy way to say whether one needs to check
m_targetElementInstance
> or shadowTreeIsValid() in these cases. I think it would be better to clear
> m_targetElementInstance.

Done. PTAL.

[pdr., 2015-09-03 19:40:28]

Wow, thanks!

LGTM

[pdr., 2015-09-03 19:40:29]

The CQ bit was checked by pdr@chromium.org

[commit-bot: I haz the power, 2015-09-03 19:40:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1323443003/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1323443003/40001

[commit-bot: I haz the power, 2015-09-03 19:45:27]

Committed patchset #3 (id:40001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201738