Remove CSS regions support, keeping a bare minimum to support "region-based" multicol.

Remove CSS regions support, keeping a bare minimum to support "region-based" multicol.

Remove everything strictly specific to CSS regions, but keep the parts that
"region-based" multicol needs. So the render flow thread framework is still around,
albeit heavily trimmed down. RenderRegion has also been kept, but is now obviously
a misnomer (to be fixed later). It serves as a base class for what css3-break refers
to as a "fragmentainer" (e.g. column, page or region). Not sure if it should really
be a renderer type, seeing that these need to be created during layout (which should
be avoided for renderers). A fragmentainer is more akin to what a line box represents
than to what a renderer does.

Additional removal and cleanup is possible, but let's start with this.

Removed everything region-specific from LayoutTests.

BUG=none

[mstensho (USE GERRIT), 2014-02-11 16:42:11]

@ojan: if you want me to dump this huge patch on someone else instead, let me
know. :)

There are more things to clean up with CSS regions gone. We can either do it
here, or file more CLs for that later, once this one has landed (which is what I
suggest).

[ojan, 2014-02-11 19:46:07]

I'll try to take a look at this soon. I'm totally fine with landing this first
and then doing followup cleanup in smaller patches.

In the meantime, CCing some others who might want to take a look and/or do the
review.

[shawnsingh, 2014-02-11 20:01:38]

for what it's worth, compositor classes (CompositedLayerMapping,
RenderLayerCompositor) are totally fine.

[pfeldman, 2014-02-11 20:43:28]

https://codereview.chromium.org/159863002/diff/1/Source/devtools/front_end/pr...
File Source/devtools/front_end/protocol_externs.js (right):

https://codereview.chromium.org/159863002/diff/1/Source/devtools/front_end/pr...
Source/devtools/front_end/protocol_externs.js:1: 
You don't want to add this file.

[ojan, 2014-02-12 00:42:46]

Actually, this patch is really hard to review. How would you feel about deleting
the tests in one patch and doing the C++ changes in a separate patch (obviously
the former would have to get committed first)?

[mihnea, 2014-02-12 04:37:10]

On 2014/02/12 00:42:46, ojan wrote:
> Actually, this patch is really hard to review. How would you feel about
deleting
> the tests in one patch and doing the C++ changes in a separate patch
(obviously
> the former would have to get committed first)?

That would be a better and easier way to do it properly - remove the tests first
and then do whatever changes are necessary to keep the fragmentation part.

[mstensho (USE GERRIT), 2014-02-12 08:57:01]

Sure, I'll file two new reviews instead. And close this one.

https://codereview.chromium.org/159863002/diff/1/Source/devtools/front_end/pr...
File Source/devtools/front_end/protocol_externs.js (right):

https://codereview.chromium.org/159863002/diff/1/Source/devtools/front_end/pr...
Source/devtools/front_end/protocol_externs.js:1: 
On 2014/02/11 20:43:33, pfeldman wrote:
> You don't want to add this file.

I certainly don't! Wonder where it came from. Some layout test having fun in my
tree?

[mstensho (USE GERRIT), 2014-02-12 10:17:15]

This has been split into:

https://codereview.chromium.org/159933010/ (removal of tests)
https://codereview.chromium.org/134473008/ (removal of code)