Refactor gpu::Buffer to allow different types of backing

Refactor gpu::Buffer to allow different types of backing

This is so that we can use either base::SharedMemory or mojo::SharedBuffer to
back gpu::Buffer.

BUG=333157
R=darin@chromium.org, viettrungluu@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=261228

[piman, 2014-04-02 01:44:56]

epenner: please review. Turns out, this looks more like your previous CL re:
gpu::Buffer refactor. meh.
viettrungluu: mojo OWNERS.

For context, https://codereview.chromium.org/221453007 is what has the other
gpu::BufferBacking implementation

[epennerAtGoogle, 2014-04-02 02:13:32]

On 2014/04/02 01:44:56, piman wrote:
> epenner: please review. Turns out, this looks more like your previous CL re:
> gpu::Buffer refactor. meh.
> viettrungluu: mojo OWNERS.
> 
> For context, https://codereview.chromium.org/221453007 is what has the other
> gpu::BufferBacking implementation

Cool. LGTM

[darin (slow to review), 2014-04-02 06:34:06]

LGTM

[viettrungluu, 2014-04-02 16:03:17]

lgtm too

[piman, 2014-04-02 17:44:26]

The CQ bit was checked by piman@chromium.org

[commit-bot: I haz the power, 2014-04-02 17:46:36]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/piman@chromium.org/213353005/20001

[piman, 2014-04-02 23:54:13]

Committed patchset #2 manually as r261228 (presubmit successful).