Merge 158839 "Reverse style resolution to avoid N^2 walk when bu..."

Merge 158839 "Reverse style resolution to avoid N^2 walk when bu..."

This change has been on trunk for 11 days, shipped in 10 canaries and presumably at least 2 dev-channel releases.  We've had no regressions/crashes reported from this CL and I believe it's the safest way to solve this issue on the M31 branch.

The merge was clean with the exception of header includes and core.gypi.  I believe this to be our safest/best option for M31.

BUG=288225
> Reverse style resolution to avoid N^2 walk when building the render tree
> 
> Blink resolves style by walking each element from first child to last, but
> when we go to insert their renderer, we look for the next renderer to insert
> before. On the initial style resolve, this means we'll walk the entire DOM
> tree trying to find the right renderer to insert before leading to an N^2
> loop over the DOM on load.
> 
> This could be fixed by changing the semantics by which we insert renderers
> (insert after instead of insert before). Instead, here I reverse the order
> we resolve style. This should ensure that in the common case, we'll find
> the renderer to insert before immediately.
> 
> Testing this change uncovered a bug in checkForSiblingStyleChanges whereby
> we'd invalidate the wrong sibling in certain cases for changed children
> of elements with directly adjacent sibling selectors. I fixed this
> and added a simplified test (acid3 caught it with this change, but it's
> a nightmare to debug).
> 
> We still attempt to process whitespace text nodes in DOM order by keeping a
> stack-allocated vector of whitespace children we postpone recalcing style on
> until the end. If we go past that limit, we process them and continue going.
> Also removing the didReattach check to force whitespace reattachment. This
> causes some whitespace layout tests results to change, but doesn't appear
> to break anything.
> 
> BUG=288225, 245478
> R=esprehn@chromium.org, ojan@chromium.org
> 
> Review URL: https://codereview.chromium.org/24350009

[eseidel, 2013-10-15 18:08:37]

Why is the whitespaceChildList.h file empty in rietfail?  Otherwise lgtm.

[leviw_travelin_and_unemployed, 2013-10-15 18:15:23]

That's weird. It's added by this patch... it should just be entirely green.

[eseidel, 2013-10-15 19:25:15]

Ready to land this with your approval Anthony.

[laforge, 2013-10-15 19:57:03]

On 2013/10/15 19:25:15, eseidel wrote:
> Ready to land this with your approval Anthony.

LGTM, w/ a cringe.