Make WebGLRenderingContext.getSupportedExtensions() return type nullable

Make WebGLRenderingContext.getSupportedExtensions()'s return type nullable

This allows it to return null when the context is lost, without resorting
to a custom binding for the method.

BUG=390780
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=177911

[Jens Widell, 2014-07-10 14:32:15]

PTAL

This is a proof-of-concept that using Nullable<T> for nullable method return
values is doable in practice.

Based on https://codereview.chromium.org/385603002/.

[haraken, 2014-07-10 14:45:17]

On 2014/07/10 14:32:15, Jens Lindström wrote:
> PTAL
> 
> This is a proof-of-concept that using Nullable<T> for nullable method return
> values is doable in practice.
> 
> Based on https://codereview.chromium.org/385603002/.

I think this is a nice change. I'll LG once the base change is landed.

[haraken, 2014-07-10 15:23:31]

The base CL looks good, so this CL LGTM as well.

[Ken Russell (switch to Gerrit), 2014-07-10 23:19:46]

LGTM if this passes the WebGL conformance tests. The test
conformance/context/context-lost.html should verify this behavior. I just
submitted some try jobs; the CQ will also run these tests.

[Jens Widell, 2014-07-11 05:53:03]

On 2014/07/10 23:19:46, Ken Russell wrote:
> LGTM if this passes the WebGL conformance tests. The test
> conformance/context/context-lost.html should verify this behavior. I just
> submitted some try jobs; the CQ will also run these tests.

Thanks. The mac_gpu/linux_gpu try jobs you triggered failed due to trying to
compile this patch without https://codereview.chromium.org/385603002/, which it
depends on.

[Jens Widell, 2014-07-11 06:29:31]

The CQ bit was checked by jl@opera.com

[commit-bot: I haz the power, 2014-07-11 06:30:36]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jl@opera.com/377113003/1

[commit-bot: I haz the power, 2014-07-11 07:42:40]

Change committed as 177911