Refactor SkGLContext to be actually extendable

Refactor SkGLContext to be actually extendable

Refactor SkGLContext to be actually extendable. Before, non-trivial subclass
would need to destroy the GL connection upon running the destructor. However,
the base class would run GL commands in its own destructor (with destroyed GL
connection)

Refactor so that SkGLContext subclass object creation is completely done by
the factory function. If the factory function returns a non-NULL ptr, it means the context
is usable.

The destruction is done with the destructor instead of virtual function called
upon destruction. Make the destructors not to call virtual functions, for
clarity.

Remove custom 1x1 FBO setup code from the base class. It appears not to be used
anymore.

BUG=skia:2992
Committed: https://skia.googlesource.com/skia/+/30bc88ccd524c0372fd2f8f79190ea4b81685beb

[Kimmo Kinnunen, 2014-10-14 12:44:09]

kkinnunen@nvidia.com changed reviewers:
+ bsalomon@google.com

[Kimmo Kinnunen, 2014-10-14 12:44:10]

Sorry to dwell on this still..

Did I misunderstand the 1x1 FBO that SkGLContext creates?

[bsalomon, 2014-10-14 14:10:08]

On 2014/10/14 12:44:10, Kimmo Kinnunen wrote:
> Sorry to dwell on this still..
> 
> Did I misunderstand the 1x1 FBO that SkGLContext creates?

lgtm

I can't remember why we had the 1x1 FBO. 

Adding humper@ in for any update the skfiddle code.

[Kimmo Kinnunen, 2014-10-15 05:24:01]

On 2014/10/14 14:10:08, bsalomon wrote:
> On 2014/10/14 12:44:10, Kimmo Kinnunen wrote:
> > Sorry to dwell on this still..
> > 
> > Did I misunderstand the 1x1 FBO that SkGLContext creates?
> 
> lgtm
> 
> I can't remember why we had the 1x1 FBO. 
> 
> Adding humper@ in for any update the skfiddle code.

Thanks. I forgot to modify the nacl part. I uploaded a new patch, would it be
possible for you to still look at that? (I'm not sure if it's 100% according to
the project conventions)

[bsalomon, 2014-10-15 14:18:23]

On 2014/10/15 05:24:01, Kimmo Kinnunen wrote:
> On 2014/10/14 14:10:08, bsalomon wrote:
> > On 2014/10/14 12:44:10, Kimmo Kinnunen wrote:
> > > Sorry to dwell on this still..
> > > 
> > > Did I misunderstand the 1x1 FBO that SkGLContext creates?
> > 
> > lgtm
> > 
> > I can't remember why we had the 1x1 FBO. 
> > 
> > Adding humper@ in for any update the skfiddle code.
> 
> Thanks. I forgot to modify the nacl part. I uploaded a new patch, would it be
> possible for you to still look at that? (I'm not sure if it's 100% according
to
> the project conventions)

Seems ok to me. The NACL thing was a project that was started and never
completed, returning NULL is fine. If it is ever revived it won't be hard to
rewrite it.

[Kimmo Kinnunen, 2014-10-16 04:56:37]

The CQ bit was checked by kkinnunen@nvidia.com

[commit-bot: I haz the power, 2014-10-16 04:56:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/640283004/100001

[commit-bot: I haz the power, 2014-10-16 05:02:25]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-10-16 05:02:25]

Try jobs failed on following builders:
  Build-Win-VS2013-x86-Debug-Trybot on client.skia.compile
(http://build.chromium.org/p/client.skia.compile/builders/Build-Win-VS2013-x86...)

[Kimmo Kinnunen, 2014-10-16 05:56:57]

The CQ bit was checked by kkinnunen@nvidia.com

[commit-bot: I haz the power, 2014-10-16 05:57:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/640283004/120001

[commit-bot: I haz the power, 2014-10-16 06:03:59]

Committed patchset #7 (id:120001) as 30bc88ccd524c0372fd2f8f79190ea4b81685beb