[chromium] Import PaintAggregator

[chromium] Import PaintAggregator
https://bugs.webkit.org/show_bug.cgi?id=53715

Reviewed by Darin Fisher.

* WebKit.gyp:
* WebKit.gypi:
* src/painting/PaintAggregator.cpp: Added.
(WebKit::calculateArea):
(WebKit::subtractIntersection):
(WebKit::sharesEdge):
(WebKit::PaintAggregator::PendingUpdate::PendingUpdate):
(WebKit::PaintAggregator::PendingUpdate::~PendingUpdate):
(WebKit::PaintAggregator::PendingUpdate::calculateScrollDamage):
(WebKit::PaintAggregator::PendingUpdate::calculatePaintBounds):
(WebKit::PaintAggregator::hasPendingUpdate):
(WebKit::PaintAggregator::clearPendingUpdate):
(WebKit::PaintAggregator::popPendingUpdate):
(WebKit::PaintAggregator::invalidateRect):
(WebKit::PaintAggregator::scrollRect):
(WebKit::PaintAggregator::scrollPaintRect):
(WebKit::PaintAggregator::shouldInvalidateScrollRect):
(WebKit::PaintAggregator::invalidateScrollRect):
(WebKit::PaintAggregator::combinePaintRects):
* src/painting/PaintAggregator.h: Added.
* tests/PaintAggregatorTest.cpp: Added.
(WebKit::TEST):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@106399 268f45cc-cd09-0410-ab3c-d52691b4dbfc