Add setNeedsLayoutAndFullPaintInvalidation to WebWidget.

Add setNeedsLayoutAndFullPaintInvalidation to WebWidget.

Plugins need to invalidate layout on their WebView when
content changes due to factors that the view is not otherwise
aware of. Here we add a method to set the various bits necessary
to cause layout to perform work at the next opportunity.

In the current code, this will be used to force paint invalidation
to be issued on the plugin when placeholder content is loaded.

BUG=472348
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=193056

[Stephen Chennney, 2015-04-02 19:06:38]

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

[Stephen Chennney, 2015-04-02 19:06:39]

This lays the groundwork for a fix to the plugin paint invalidation problem. I
believe it is also necessary to fix the not-yet-landed layout for plugins
Chromium patch.

We need this in before the branch point or we'll have to revert the plugin paint
invalidation patch, thus disabling Slimming Paint perf tests.

[Stephen Chennney, 2015-04-02 19:07:13]

+tommycli

[Stephen Chennney, 2015-04-02 19:07:20]

The CQ bit was checked by schenney@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-04-02 19:08:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1056893003/20001

[commit-bot: I haz the power, 2015-04-02 19:19:05]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-04-02 19:19:06]

Try jobs failed on following builders:
  blink_presubmit on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/blink_presubmit/builds/3...)

[pdr., 2015-04-02 19:45:38]

On 2015/04/02 at 19:19:06, commit-bot wrote:
> Try jobs failed on following builders:
>   blink_presubmit on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/blink_presubmit/builds/3...)

LGTM

[Stephen Chennney, 2015-04-02 19:59:55]

The CQ bit was checked by schenney@chromium.org

[commit-bot: I haz the power, 2015-04-02 20:00:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1056893003/20001

[commit-bot: I haz the power, 2015-04-03 00:12:36]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=193056