Defer clearing textures and renderbuffers

Defer clearing textures and renderbuffers

Textures and Renderbuffers are now cleared at the
last possible moment. This allows them to be cleared
only when absolutely necessary.

TEST=unit tests
BUG=99554
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=108226

[greggman, 2011-10-29 03:13:33]

Hey Al, please review.

Sorry, it's so big 

Some notes:

Attachment:ValidForAttachemntType needs to be filled out. Added an issue for
that
http://code.google.com/p/chromium/issues/detail?id=102232

I didn't know how to name SafeToRender. It used to be called Cleared but there
are 2 kinds of cleared. Cleared for all the mips that will be used and Cleared
for any particular mip.  Example. Set mips to 4x4, 2x2, 1x1, 16x16. That last
mip isn't used so even if it is not cleared it is SafeToRender.

If you have a better name for rather than "SafeToRender" I'm happy to change it.

[apatrick_chromium, 2011-11-01 18:39:25]

Arg. Well it _looks_ right! LGTM.

[commit-bot: I haz the power, 2011-11-02 00:07:00]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/gman@chromium.org/8341128/5002

[commit-bot: I haz the power, 2011-11-02 01:32:21]

Change committed as 108226