glDiscardFramebuffer() in GrGpuGL::discard uses invalid GLenum

glDiscardFramebuffer() in GrGpuGL::discard uses invalid GLenum

According to the spec:

  "If a framebuffer object is bound to <target>, then <attachments> may
  contain COLOR_ATTACHMENT0, DEPTH_ATTACHMENT, and/or
  STENCIL_ATTACHMENT.  If the framebuffer object is not complete,
  DiscardFramebufferEXT may be ignored.

  If the default framebuffer is bound to <target>,
  then <attachment> may contain COLOR, identifying the color buffer;
  DEPTH, identifying the depth buffer; or STENCIL, identifying the
  stencil buffer."

Do the same as in glInvalidateFramebuffer() case.

Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>;

R=bsalomon@google.com
BUG=skia:2411
Committed: http://code.google.com/p/skia/source/detail?r=14220

[bsalomon, 2014-04-15 14:38:49]

On 2014/04/14 08:20:31, samuelig wrote:

lgtm, but can you change the tabs to 4 spaces?

[siglesias, 2014-04-15 14:40:07]

On 2014/04/15 14:38:49, bsalomon wrote:
> On 2014/04/14 08:20:31, samuelig wrote:
> 
> lgtm, but can you change the tabs to 4 spaces?

Oops! Yes, I will do that.

[siglesias, 2014-04-16 08:39:01]

On 2014/04/15 14:40:07, samuelig wrote:
> On 2014/04/15 14:38:49, bsalomon wrote:
> > On 2014/04/14 08:20:31, samuelig wrote:
> > 
> > lgtm, but can you change the tabs to 4 spaces?
> 
> Oops! Yes, I will do that.

Done

[bsalomon, 2014-04-16 13:23:11]

The CQ bit was checked by bsalomon@google.com

[commit-bot: I haz the power, 2014-04-16 13:23:23]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/siglesias@igalia.com/236193007/20001

[commit-bot: I haz the power, 2014-04-16 14:33:30]

Change committed as 14220