Amazon.com Additional Information links aren't clickable

Amazon.com Additional Information links aren't clickable
https://bugs.webkit.org/show_bug.cgi?id=151401
<rdar://problem/23454261>

Reviewed by Darin Adler.

Source/WebCore:

The cause of this issue is that the painting order is different from the hittest order so we can end up
with visible but unreachable content. To fix this, the executation flow of hittest has been reordered.
According to the paint system, which renders the webpage from the bottom RenderLayer to the top, contents
are rendered before floats. Hence, for the hittest, which determines the hitted location from top RenderLayer
to the bottom, should do it reversedly. Now, hittest will first test floats then contents.

Test: fast/block/float/hit-test-on-overlapping-floats.html

* rendering/RenderBlock.cpp:
(WebCore::RenderBlock::nodeAtPoint):

LayoutTests:

* fast/block/float/hit-test-on-overlapping-floats-expected.txt: Added.
* fast/block/float/hit-test-on-overlapping-floats.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@192854 268f45cc-cd09-0410-ab3c-d52691b4dbfc