Merge 129511 - [chromium] adding a page overlay causes endless update loop when accelerated composi…

Merge 129511 - [chromium] adding a page overlay causes endless update loop when accelerated compositing is used
https://bugs.webkit.org/show_bug.cgi?id=97466

Reviewed by James Robinson.

Do not update overlays in composite() -- doing so ultimately causes invalidation
of the view, hence another update and another call do composite(). Overlays should be
updated only when their content changes.

* src/WebViewImpl.cpp:
(WebKit::WebViewImpl::composite):

TBR=caseq@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=132049