Rename discardFramebufferEXT to discardBackbufferCHROMIUM to avoid collision with real discardFrame…

Rename discardFramebufferEXT to discardBackbufferCHROMIUM to avoid collision with real discardFramebufferEXT

Calling the (real) discardFramebufferEXT in the compositor is a performance win, at least on tilers. However
currently it can't be called because we alias the name for a different API that controls backbuffer
allocation, which I don't want to change.  This renames the code to make backbuffer control a completely
separate API so I can pipe GL_EXT_discard_framebuffer in fully as a follow-up.

Depends on https://bugs.webkit.org/show_bug.cgi?id=104316

BUG=


Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=171908

[piman, 2012-12-07 01:48:08]

lgtm

[Ken Russell (switch to Gerrit), 2012-12-07 04:24:55]

lgtm

[commit-bot: I haz the power, 2012-12-07 19:16:45]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jamesr@chromium.org/11474014/1

[commit-bot: I haz the power, 2012-12-07 19:37:26]

Sorry for I got bad news for ya.
Compile failed with a clobber build on android_clang_dbg.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=android_cl...
Your code is likely broken or HEAD is junk. Please ensure your
code is not broken then alert the build sheriffs.
Look at the try server FAQ for more details.

[commit-bot: I haz the power, 2012-12-07 22:02:23]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jamesr@chromium.org/11474014/3002

[commit-bot: I haz the power, 2012-12-08 01:29:42]

Change committed as 171908