Add a setNeedsLayout method to WebPluginContainer.

Add a setNeedsLayout method to WebPluginContainer.

This allows us to lazily propagate a full layout lifecycle update request for a plugin to the container. Previously, there was no way to indicate a need for a lifecycle update other than paint invalidation. This was a bug, since paint invalidation does not trigger layout, and as a result we could end up with a plugin that tries to paint with stale layout.

https://codereview.chromium.org/1158693002 will make use of this CL to replace a call to invalidate() with setNeedsLayout().

BUG=436562
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=195908

[chrishtr, 2015-05-25 23:57:50]

chrishtr@chromium.org changed reviewers:
+ schenney@chromium.org, wangxianzhu@chromium.org

[Stephen Chennney, 2015-05-26 13:08:52]

Definitely LGTM.

[Stephen Chennney, 2015-05-26 13:09:01]

The CQ bit was checked by schenney@chromium.org

[commit-bot: I haz the power, 2015-05-26 13:09:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1157943002/20001

[commit-bot: I haz the power, 2015-05-26 13:12:18]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=195908