Remove SkShader virtual method validContext

Remove SkShader virtual method validContext

patch from issue 267923005

BUG=skia:

Committed: http://code.google.com/p/skia/source/detail?r=14573

[scroggo, 2014-05-05 16:02:47]

All of my comments in https://codereview.chromium.org/267923005/ have been
addressed, except for the following:

- SkComposeShader needs to handle alpha (at least in the broken way it did
before)

- compose alpha needs to call the context destructor for one context if the
other one failed.

https://codereview.chromium.org/261773005/diff/40001/src/core/SkBlitter.cpp
File src/core/SkBlitter.cpp (right):

https://codereview.chromium.org/261773005/diff/40001/src/core/SkBlitter.cpp#n...
src/core/SkBlitter.cpp:1047: SkNEW_PLACEMENT_ARGS(fShaderContext,
SkTransparentShaderContext, (*fShader, rec));
Can't this just be an SkShader::Context? It seems like this new implementation
(which happens to sound like the context for SkTransparentShader, but behaves
differently) will never be called, so it doesn't actually need to do anything.

[reed1, 2014-05-05 18:27:21]

ptal

[scroggo, 2014-05-05 18:31:13]

lgtm

[reed1, 2014-05-05 18:31:42]

The CQ bit was checked by reed@google.com

[commit-bot: I haz the power, 2014-05-05 18:32:11]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/reed@google.com/261773005/60001

[commit-bot: I haz the power, 2014-05-05 18:39:27]

Change committed as 14573

[mtklein, 2014-05-06 13:08:47]

On 2014/05/05 18:39:27, I haz the power (commit-bot) wrote:
> Change committed as 14573

Valgrind says,
http://108.170.220.120:10117/builders/Test-Ubuntu12-ShuttleA-GTX550Ti-x86_64-...

That is, PictureShader is leaking its underlying BitmapShader.  This CL is the
likely culprit.  Is it possible the Context* is not being deleted?

[scroggo, 2014-05-06 14:51:01]

On 2014/05/06 13:08:47, mtklein wrote:
> On 2014/05/05 18:39:27, I haz the power (commit-bot) wrote:
> > Change committed as 14573
> 
> Valgrind says,
>
http://108.170.220.120:10117/builders/Test-Ubuntu12-ShuttleA-GTX550Ti-x86_64-...
> 
> That is, PictureShader is leaking its underlying BitmapShader.  This CL is the
> likely culprit.  Is it possible the Context* is not being deleted?

reed@ has submitted what he believes to be the fix here:
https://codereview.chromium.org/269163004

Watching it go through the buildbots...