[CSS Blending] SVG overlapping elements within a group don't blend together.

[CSS Blending] SVG overlapping elements within a group don't blend together.

For a group of overlapping elements in an SVG, if mix-blend-mode is
specified on the group, the intersection of any overlapping elements also
incorrectly blends. This patch addresses the issue.
The problem is similar to https://codereview.chromium.org/104663003/

BUG=229615
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=164504

[mitica, 2013-12-20 12:56:45]

Hi Dirk, Stephen,

Can you please have a look over this patch?

Thanks!

[Stephen Chennney, 2013-12-30 16:31:54]

LGTM but please deal with the test case before submitting (or put up a follow on
patch).

I recognize that the description is helpful, but we would like to keep test
cases to the tested content only to avoid extraneous failures.

https://codereview.chromium.org/98543012/diff/1/LayoutTests/css3/compositing/...
File LayoutTests/css3/compositing/svg-blend-overlapping-elements.html (right):

https://codereview.chromium.org/98543012/diff/1/LayoutTests/css3/compositing/...
LayoutTests/css3/compositing/svg-blend-overlapping-elements.html:4: <p>Test
mix-blend-mode on a group consisting of overlapping elements. <br/>
Could you change this to be a comment rather than text in the test. We've had
issues with flaky test failures when there is text in ref tests, so we try to
avoid it if not relevant to the tested code.

[commit-bot: I haz the power, 2014-01-06 09:51:57]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mitica@adobe.com/98543012/70001

[commit-bot: I haz the power, 2014-01-06 11:27:24]

Change committed as 164504