Allow tests to stub out GL draw calls.

Allow tests to stub out GL draw calls.

This allows us to use real GL bindings but without drawing when we
don't care about pixel output, allowing for faster execution. In
particular this will allow us to use OSMesa instead of a completely
fake GL implementation in the compositor for browser tests.

We add a new kDisableGLDrawingForTests command line flag that can
be set to prevent the GL draw calls from doing any work. We will be
able to set this flag in the browser test environment for any tests
that don't require real pixel output.

R=piman, sievers
BUG=270918
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=244405

[danakj, 2014-01-10 22:58:41]

Here's a CL with just the stub draw calls in it. I'll make use of it for browser
tests separately.

Daniel mentioned he'd prefer a name NullDraw over Stub so I can go thru here and
name-replace. If you have an opinion piman can you let me know?

[danakj, 2014-01-10 23:09:34]

Patch set 2 renames to NullDraw

[piman, 2014-01-11 00:54:17]

lgtm

[commit-bot: I haz the power, 2014-01-11 19:25:06]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/danakj@chromium.org/132473009/40001

[commit-bot: I haz the power, 2014-01-12 02:09:48]

Change committed as 244405