Move RenderSVGResource into the inheritance hierarchy

Move RenderSVGResource into the inheritance hierarchy

With RenderSVGResource reduced to a common base for paint-servers,
it's possible to get rid of the multiple inheritance on
RenderSVGResourceContainer by instead making it the base of
RenderSVGResource{Gradient,Pattern} while inheriting from
RenderSVGResourceContainer.
Rename the files appropriately and update existing references to
RenderSVGResource. Also take the opportunity to tighten the types
a bit in some places.

BUG=420022
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=184278

[fs, 2014-10-23 12:25:42]

fs@opera.com changed reviewers:
+ fmalita@chromium.org, pdr@chromium.org, schenney@chromium.org

[f(malita), 2014-10-23 13:48:11]

Thanks for pursuing this cleanup, LGTM!

[fs, 2014-10-23 14:19:29]

The CQ bit was checked by fs@opera.com

[commit-bot: I haz the power, 2014-10-23 14:20:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/673753004/20001

[fs, 2014-10-23 14:22:12]

The CQ bit was checked by fs@opera.com

[fs, 2014-10-23 14:22:19]

The CQ bit was checked by fs@opera.com

[fs, 2014-10-23 14:22:20]

The CQ bit was unchecked by fs@opera.com

[fs, 2014-10-23 14:24:43]

On 2014/10/23 13:48:11, Florin Malita wrote:
> Thanks for pursuing this cleanup, LGTM!

@fmalita: This might conflict a little bit with
https://codereview.chromium.org/453653003/ so I'll let that land first.

[f(malita), 2014-10-23 14:27:04]

On 2014/10/23 14:24:43, fs wrote:
> On 2014/10/23 13:48:11, Florin Malita wrote:
> > Thanks for pursuing this cleanup, LGTM!
> 
> @fmalita: This might conflict a little bit with
> https://codereview.chromium.org/453653003/ so I'll let that land first.

thanks :)

[f(malita), 2014-10-23 15:30:11]

The CQ bit was checked by fmalita@chromium.org

[commit-bot: I haz the power, 2014-10-23 15:31:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/673753004/20001

[commit-bot: I haz the power, 2014-10-23 15:32:27]

Committed patchset #2 (id:20001) as 184278