When style changes, set the LayoutObject as a client for all StyleImage loads.

When style changes, set the LayoutObject as a client for all StyleImage loads

We have logic to dynamically change an image load's
ResourceLoadPriority based on whether it is in the viewport. We would like
to generalize this logic to support other types of resources and other
factors for priority. To do that, we need to ensure every image that might
be in the viewport is associated with a LayoutObject, so that it can pull its
priority state, rather than having the LayoutObject push the state.

We have not been consistent about ensuring that every LayoutObject registers
itself as a client with every StyleImage in its ComputedStyle. This change
ensures that we do so.

BUG=536147
Committed: https://crrev.com/c5ce89c70400c6165fade1c9f40dae2543cbc89b
Cr-Commit-Position: refs/heads/master@{#350946}

[Nate Chapin, 2015-09-23 19:34:44]

japhet@chromium.org changed reviewers:
+ esprehn@chromium.org

[Nate Chapin, 2015-09-23 19:34:44]

This is the post-merge continuation of
https://codereview.chromium.org/1342503002/

[esprehn, 2015-09-25 20:05:21]

lgtm, is there a bug associated with this? Can you expand the description for
why this is important? How did image invalidation work before?

[Nate Chapin, 2015-09-25 20:14:14]

On 2015/09/25 20:05:21, esprehn wrote:
> lgtm, is there a bug associated with this? Can you expand the description for
> why this is important? How did image invalidation work before?

Bug created and referenced, change description expanded.

[Nate Chapin, 2015-09-25 22:21:02]

The CQ bit was checked by japhet@chromium.org

[commit-bot: I haz the power, 2015-09-25 22:22:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1362693004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1362693004/1

[commit-bot: I haz the power, 2015-09-25 23:34:20]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-25 23:35:30]

Patchset 1 (id:??) landed as
https://crrev.com/c5ce89c70400c6165fade1c9f40dae2543cbc89b
Cr-Commit-Position: refs/heads/master@{#350946}